Hello and welcome to this guide to They are Billions.

As you most certainly know - reading this guide and all They are Billions is a RTS game set in a zombie infested world with an emphasis on survival and which features a pausable gameplay. Therefore it is quite logical that certain strategies will be more fruitful than others and I am here to give you a step by step guide to allow you to defeat the first map and teach you skills that can be used across all your games and all the maps so you can achieve victory.

But why should you be listening to me?

Well, first, I've got access to all maps currently avalaible to play and I can systematically win on any playthrough at the regular setting levels (more on that later).
Moreover, as I'm writing those pages, I have over 100 hours of gameplay which is all things considering quite a lot considering the short time that the game has been avalaible.

Why are you here?

Most likely, you are here because you are still inexperienced and can't seem to manage to beat the game at settings necessary to unlock the second level. Or perhaps you are simply looking for more tips and advice to become more skillful at playing the game. Or for any other reasons. In any case you are very welcome!

If you are in the first case however, despair not! I've only beaten the first level after dozens of tries! But once I did it only took a couple attempts to unlock the third map and only one attempt for the fourth.

So relax, take a deep breath and let's go, shall we?

Note

This guide is currently a work-in-progress and the information present here may be incomplete and subject to change due to the Beta nature of the game. I will try my best to complete the guide as soon as time allows me to. And I will update the guide as more game updates come into play in what I hope is a reasonable schedule.
Comments are always appreciated as well as any remarks on mistakes I might have made (English not being my native tongue).

Thank you for your time and I hope this guide will be instructive for you.

Perhaps you feel like you already know how to start a new game and you know that you need at least 100% difficulty to unlock the second map.

But did you know that the 100% difficulty (that is Medium Population and 100 Days) is actually harder than the 130% difficulty (Brutal Population and 120% Days).



You see the game difficulty does not come from the amount of zombies present at the beginning of the game. Nor does it come from the amount of zombies contained in each wave. Nay! It comes from time.

Time is your biggest foe - someone famous once said. Time is the essence of the game. The faster you can achieve something, the better your colony will fare. The more time you have, the better you will do.

Brutal Population will only delay your ability to expand early game and to clear the map early of any zombie by a factor of a few days. However the extra 20 days to prepare will be essential for your survival. 20 extra days at the end of the game, ages after you've cleared the map will bring you tons of ressources, which will allow you to build tons of defenses. It's as easy as that.

So let's forget about the 100% difficulty factor and start the game with a 130% factor. Trust me on this one.

Step 1: Scout

At the start of the game, pause the game. Always.
You start the game with your command center, 4 rangers and 1 soldier. Your first priority is to scout.
Use your rangers, as the have faster line of sight (referred from now on as LoS) and movement speed and order your rangers to go in separate directions, so as to cover as many ground as possible in as little time as possible.
The goal of scouting is simple: you want to know if you have a good map (see Do I have a good map?)to survive the early game and you want to know where you can expand.

Before unpausing the game:
Build a food building (fisherman if possible, cottage hut if not) where you can (the more food the better, unless building it will block the best ratio of wood on the treeline).

Then unpause the game and start exploring in concentric circles around your base until you find zombies in all directions.

Each time you get a cash inflow: pause and build some houses. As soon as possible, put your soldier close to your house in a patrol mode so as to avoid any surprise.

When you've finished scouting (and can no longer scout without running into zombies), put your rangers back in patrol mode to protect your colony and start killing some zombies.


A good map is qualified by a few factors:
-Plenty of grasslands and lakes to build your food industry.
-Plenty of black terrain to build your houses and other buildings.
- At least 2 areas where you can collect wood.
- At least one good stone deposit (5+) (Optional).
- Some chokepoints at the edge of your previsional expansion area.

Moreover some elements will make it a great map if:
- You find plenty of goodies laying around, especially 20 stones and gold.
- You have an incredible amount of land to expand into.
- There is only very few options to access to your command center AND you have some options to extend (if not then it is a very poor map).

As you can see the keyword is space. You want space to expand as it will allow you to boom your economy, which means more ressources avalaible and more troops to expand overall (as well as more defenses).

A note on the limitations of early game scouting

Some of you must be wandering. Wait a minute. When should I stop scouting?
Perhaps now you are expecting me to say: NEVER! But I won't.

You stop scouting when you encounter this:



The City of Doom. Don't get close to there in the early game. If you spawn too close to one (if you can see one with your screen centered on your Command Center and zoomed out: start over until you know what you are doing. I once managed to win a game with 3 Cities of Doom close-by but that's a story for another day and another map.

Also if you can't scout without running into runners (see what I did there?): Stop.
Always come back circling back when you are being chased by runners so you don't accidentally (or intentionnaly but who would do such a thing!) bring them to your base.


The role of scouting is to know where to expand so....



How do you know where to expand? How do you know where to stop in the early game?

The key phrases here are: Do not bite more than you can chew. and Be brave, be bold, be decisive.

You don't want to overextend and be unable to defend your base. However you don't want to underextend and be stuck in a position where your economy will struglly.

I won't lie to you, it is very dependant on the map, your experience and if you are feeling risky or not.

A few pointers to guide you:
- Be mindful of chokepoints. They can be a great ally in your efforts to repel the zombie onslaught.
- Don't go into open areas you can't protect (unless you have no choice). If you can't see any chokepoints around an area and zombies are as far as you can see, then perhaps you shouldn't expand that way (unless it is the only way...).
- Don't go too close to Cities of Doom. YOU WILL DIE (unless you have ballistas or a significant army).
- Be mindful of ressources. Expanding towards ressources is usually what you want to do.

Mayor Time

As soon as you build a sufficient amount of houses, you will be greeted by the election screen.
This election screen will give you the choice between two mayors with different bonuses attached to them.
The bonuses can go from extra ressources (as evidenced by my screenshot) to units, a research, building or even specific bonuses for specific buildings (+ energy for Windmills for example).

Sometimes the choice is a no brainer. Somtimes the choice will be hard. Most often than not you will have to make a decision between the early game and the late game, or between defenses and economy.

I would rank those choices as follow:
Late game>Economy>Early game>Defenses.

To give you a concrete example with Mayor bonuses you could have:
+ Energy to Mills>1000 gold>2 rangers>10 Walls and a Gate.

Here my choice was a no brainer. I had to go for the stone as not only will it allow me to delay my quarry, but it also allowed me to build the soldier center by Day 1. A strategy that I will explain in the next step.

Step 2: What buildings to rush?

Some people will tell you that the best building you could build early is the Wood Workshop. They will tell you to build it as soon as you can and as soon as your fledgling economy can allow.
They are wrong! So wrong! (Sorry guys)

The best building you can rush is the mighty Soldier Centre:


Here's the thing with the Soldier Centre. It creates Rangers. That's it. That's all you need in the early game. Pump out some rangers as soon as you can, expand and start clearing the map.
More map cleared = more economy = more gold = more time with a better economy = better chances to win.
That is why the choice between the two mayors in my playthrough was a no brainer.
You need 20 stones and 20 wood to build the Soldier Center (and 450 gold).
The stones are the hardest to come by and can only be easily found through scavenging goodies (it's rare to find 20 stones though it happens) and by the mayor election.
Finding the stone needed through this means will allow you to build the Soldier Center by day 2.
Your other option, which is still a viable option, is to build a quarry and tediously wait for your stone to be extracted. It will delay your Soldier Center by at least 2 days. Another issue raised by the quarry is that Stone does not become an important ressource until later in the game and you will have to manually deactivate your quarry once it has reached the cap.

Once the Soldier Center is built, you should build 1 Ranger at a time each time you can (only 1 Ranger at a time so you can spend your ressources elsewhere in the mean time). Expand your colony by building more houses, a windmill and more food buildings. Keep an eye on your population count as you need to have at least 10 to build the Wood Workshop which is the next objective.
Expanding your wood production is also a good way to spend your gold. It will allow you to build Tesla Towers and early wooden walls.
But don't let your wood reach 50 without either deactivating your sawmills or building some walls and Tesla Towers. Don't build wooden towers on defense. Use the patrol mode.

Techs

By Day 6, you can have the Wood Workshop and be in the process of deciding which tech to go for. Depending on how the game goes, you may delay this building by a few days but do not exceed Day 12 or you might be in trouble.

The most important techs are as follow:
Cottage Houses, Farms and Market.

If you have not build a quarry perhaps you should now consider it for the sole purpose of building a market later in the game.

The tech you will choose will depend on certain factors and the way the map is shaping your playstyle. Here are the pros and cons of each tech as well as in what situation you should choose them:

Cottage Houses: You find yourself drowning in food or lack the space to expand reasonably well because of the terrain constriction. As you lack space to build houses, researching Cottage Houses first is a reasonable choice. Be careful to have enough of a wood production to be able to keep up with the upgrading process.

Farms: You have too much space and not enough fertile lands or lakes to be able to keep up with your compulsive need to build houses (which in the game is a good compulsive need). You still have some spots where you could build farms to keep up with your expansion. Most of the time this is my case and I go with Farms first.

Market: You both have space and plenty of food. Moreover you happen to have an abundance of wood and stone around and you need to start selling as you are tired to manually pause and unpause buildings. In addition, you happen to have 40 Wood and 40 Stones laying around that you don't know how to use. It's very rare to start with the Market tech but when you do, it usually means you are in a great spot.

Time to prepare

By day 12, you should actively be preparing for the first wave.
By this time you should have:
- A good enough economy.
- Some sections cordonned off by walls and patrolled by one or two rangers.
- A dozen or so rangers actively chasing zombies.
- Have delimited in your head a first perimeter towards which expand and that you can reach by Day 16.

The first wave is still a few days off so you have time but you should get to it right away.

What is a good defence for Wave 1?

The first wave is quite weak and can easily be fended off by a two layered wooden walls and your rangers.
So in essence you only need:
-2 layers of walls (though 1 might suffice, better safe than sorry). Note that you can build the second layer right as the second wave spawns so don't fret and waste your ressources on doublind the walls everywhere.
- 10 or so rangers.

What you don't need:
- Towers. They are bad. Don't build them. They cost a lot and do not offer you a lot of fire power.
- Traps. Don't research them. They are gold intensive, break easily and cost too much to repair.
- Soldiers. Sure bring your lone soldier to help but don't train anything but rangers. Soldiers will never be really useful in the game (or if they are useful, other units will outclass them) so it is not relevant to train them.

What you may consider:
- Ballistas. Your gold and wood is better spent elsewhere as of now but if the only mayor bonus you managed to secure was a ballista then wait to use it when you know where the first wave is gonna hit. Or if your economy is so good that you can spare researching and building one before the first wave, then go for it. You will need them eventually.
- Snipers. If you find yourself flowing in gold because of goodies laying around or your incredible booming skill AND that you have a bit of iron laying around, then go for it. Snipers have been made incredibly useful thanks to the latest patch that allows units to switch between targeting the closest ennemy and the strongest. You may need some in the late game to cover your rangers before you get Titans if you encounter Spitters. Therefore training them early could be useful (though they have high upkeep and are more than twice as expensive to produce). However they will not be immediately incredibly useful as chances are you won't encounter many spitters early (or you are one unlucky bastard).

An example of a defense that will hold the first wave:





Once the first wave is beaten then you are ready for Step 3.

Here I will discuss:
- the need to continuously expand.
- how to defend your base efficiently.
- how to boom your economy.


Now that the first wave has been defeated, it is time to expand. Form up a killing squad of rangers and kill all the infected in the area you want to expand towards. Avoid the cities of doom.

You shouldn't stay on the defensive as it will only serve to waste precious time. You want to always expand your land as more land means more buildings means more economy.

Go one area at a time and focus your needs. Let's take an example:
Your base is at the center of the map but you need more food. Eastwards: large arable lands. Westwards, a desolate fields with patches of stone. Northwards, some arable lands and patches of wood that forms a nice chokepoint. Southwards, desolate lands with no ressource on sight and hordes of zombies. Where do you expand? You say Eastwards? Wrong! There's a city of doom there. Oh? I forgot to mention it? My bad.
Expand Northwards as the food and the wood will allow you to upgrade your tents into Cottage Huts.
The obvious solution is not always the best.

A good rule of thumb is to expand towards area you can defend. Vast expanses of ressources are worthless if they are endlessly swamped by zombies: You will only waste your ressources.


After Wave 2, a lone ranger patrolling your walls is no longer enough. You want Ballistas. You need Ballistas. At least one on each outer layer.
Why you ask? Well, after Wave 2, the game starts sending what I call mini-hordes. Mini-hordes are unannounced hordes, much smaller than the horde that comes with the waves (20ish infected usually), but which can pose problem. Just like regular hordes, they come from the edge of the map and make a beeline for your Command Center. Unlike regular hordes though, they come from all directions and thus your base needs to be defended in all directions. A single ballista is enough to deal with them, otherwise a few rangers will do the trick as well.

Here I will discuss:

- Why is it important to clear the map of infected.
- The most viable strategies to do so.
- How to deal with Cities of Doom and their economic value
- How to continue to expand.

You expand. As rapidly as possible.Build Tesla Towers protected by a few units (as mini hordes may still come from the edge of the map) and go towards the edges of the map where you will build your defenses (see Defense Layout to know how to build them). In the area between your previous layer and the edge layer, boom like crazy: houses, markets, banks, mines, farms, etc. Go nuts. Be sure to build plenty of Mills as you will need the energy but if you see a nice flat area where you can place many stone houses, then consider a market and a bank. Remember you can only build 3 Markets and 3 Banks in a game so it's best to maximize the area they cover.

Expanding on a nice fertile area:



Not expanding and turtling would be your biggest mistake. In order to keep up with someone who expand you would have to maximize the space you already have and thus upgrade everything to Advanced Buildings. Yet you do not want to do so. It may seem counterintuitive but it is always better to build a new Farm rather than upgrading a farm already built. The new farm will produce just as much food but will consume less energy and less upkeep. Eventually you will run out of place and you may upgrade them.
It may sometimes be good to upgrade mines but only in very ressource scarce maps or if you have a huge income and are forced to buy from the market. However the same advice goes as to the farms. It is best to build a new mine rather than upgrade an existing one. Also you only want to upgrade the mines that offer you the best ratio of ressources of course.
As for Mills, don't bother upgrading them. Their upkeep is off the roof when upgraded and you do not get that much Energy comparatively. You are better off building a power plant.

Also be sure to build defenses. A map cleared of infected does not mean a safe map. As I've stated previously, hordes and mini hordes may spawn from the edges of the map and ruin your day. Don't neglect your safety or rebuilding will set you back significantly.


They are Billions is a game that offers a lot of strategical choices as the defenses you could use. Ballistas, Executors, Walls, Traps, Shocking Tower, Towers and Units.
Unfortunately, as per the game being early accessand still unbalanced, I have found that there is only
one type of defense that is truly effective: Executors and Stone Walls.That's it. That's all you need.
Here let me explain to you why:

The shocking tower seems really nice doesn't it? Decent AOE turning all infected in the area to dust and a decentish attack speed. It is excellent to deal with the previous waves as most of the infected are regular infected. However during the final wave they will be useless.
First off, Shocking Towers do not kill some infected in one hit: Executive Infected requires 2, Chubbies almost 10 hits, Harpies 2. That means that they can get close and deal some damage to the wall and eventually destroy the Tower. Sure that would be the case with any defense against a sufficient amount of infected, however Shocking Towers are specially vulnerable to Harpies (which can jump over walls and 2-3 harpies can destroy it before it can deal sufficient amount of damage) and Spitters which do not even enter the range of the Shocking Tower! To make them effective you have to place them on the frontline so as to maximize their AOE meaning they will be targeted by spitters first. Morever and to top it all, Shocking Towers are quite expensive to maintain as they cost a whopping 30 energy! Don't build them.

Traps seem good too. I mean they slow and damage the infected, what more would you want? Well traps have one big disadvantage; they break and quite fast too! During the final horde, the blade traps may last you 10-15 seconds at most, which is ridiculous as you will have to hold for a few minutes. Their efficiency is quite limited, they are very costly to build and to repair so do not build them. Moreover Blades Traps require iron and quite frankly your iron is better spent elsewhere.

Since the patch allowing units and defenses to change their target priority, Stone Towers may seem viable. I haven't fiddled around with them that much since last patch but a few well placed towers could be useful. However they have quite a lot of disadvantages; they are expensive, you need units to garrison in them and they don't offer potent bonuses (Extra range wont be that effective as the zombies will be right to your face). In my humble opinion, towers seem a bit meh.

So what does work, you ask?



This works. As many executors as you can fit, followed by two layers of stone walls and then another layer (diagonal walls allow you to place them as in the screenshot but vertical and horizontal walls will require a gap between the two.

Here's another example:



It's a very simple design albeit a very effective one. The infected will eventually go through with significant time and number but you shouldn't have only one layer of this defenses but many that you would have built as you expanded and upgraded right before the final wave. At brutal pop, 3 layers should be enough to guarantee a survival but be sure to have a few titans laying around to colmate any breach.


The short answer is as late as possible. The final wave will spawn around Day 113

Day 114, the waves are pushing towards the walls.
Therefore, you want to stop booming at least 6 days before that and reinforce your defenses. In fact it greatly depends on the state of your defenses. In this playthrough, I stopped booming at Day 100 and started building defenses before realizing that I could have boomed a little longer to allow me to build more defense (I was short on money by Day 107). The fact was that my defenses were in great part already in place and thus I only had to upgrade 40ish ballistas.
There is no definite answer as to when to stop booming but I would say that by Day 106, you should start thinking about reinforcing all your defenses.


Reinforce your defenses


Typical City ready for the final wave (look at the mini-map)


Quite frankly, nothing. If you've built your defenses correctly, then they will take care of everything for you. I see many people saying that you should place a few titans at every chokepoints and pause often to manually target spitters. I never do.
What I do is to keep all my titans at one point (the point I think is the most vulnerable) and then move them if I feel another area is weakening. Then at the end I put them in Chase mode to mop up any remaning zombies.
However be sure to pause often and check the state of your defenses. A breach may quickly appear. If such a breach appear, be sure to manually to build additional layers of walls to slow them down.

You are now ready, Good Luck!

Introduction

Some of you have expressed their interest on what to research, what is useful and what isn't.
Here's an attempt to answer your concerns.

First off what you need to know is that not all research are useful. Some of them are simply a waste of money, others are situational and finally some are a must buy.

I will rank those technologies per usefullness (Rank S to D) and per tech level (Wood, Stone and Foundry).

Here's a legend for the different ranks:
Rank S: Must have. Those researches need to bee lined for as soon as possible.
Rank A: You will research those technologies in almost every single game but you can take your time in getting them depending on the situation.
Rank B: You may choose not to research those technologies but most of the time you will anyway.
Rank C: Those are meh technologies, without really any appeal except in very specific situations or for fun factor.
Rank D: The worst tech. Those are bad and you shouldn't research them as they are a waste of money.

Tech 1: Wood Workshop

• Rank S: Cottage Houses: Better houses. Less space. More gold. A must have ASAP.
  
• Rank S: Farms: More food for more houses for more gold. Same as the research above.
  
• Rank A: Ballistas: The best early game defense. You may wait Day 20+ before starting to build some though as soldiers will be enough to repel the wandering hordes.
  
• Rank A: Market: More food. More gold thanks to ressource selling and you won't have to worry about overproducing any ressource except gold.
  
• Rank A: Stone Workshop: You may wait until you have too much gold to start building it.
  
• Rank B: Snipers: You can skip those if you want but they can help clearing the map before the titans. They are especially good at killing spitters by putting them on the auto-targeting mode "Strongest ennemies first".
  
• Rank C: Lookout Tower: Very situational. It is useful to build one before expanding on one direction if you don't have a lot of troops and if you think you may be too close to a City of Doom so as to avoid being overrun. Most of the time useless.
  
• Rank D: Wooden Spikes: Too expensive and not really useful. Avoid them.

• Rank S: Banks: More gold. Enough said. Rush build it for a significant boost in your economy.
  
• Rank A: Stone Houses: Same as the Cottage houses, Stone Houses offer more buck for less space. They do cost a lot of stone and chances are you won't have enough stone to spend when you unlock this tech.
  
• Rank A: Stone Walls: The best walls so far. They cost a lot of stone though when build in bulks or when upgrading wooden walls. Upgrading Stone Houses should be prioritized.
  
• Rank A: Foundry: You need to build the Foundry quite early (Day 40+).
  
• Rank B: Power Plant: Consume Stone that you need for Stone Houses and Stone Walls. Prioritize building Mills or expanding so as to build Mills before choosing the route of the Power Plant.
  
• Rank C: Stone Tower: Good in chokepoints as they have a lot of HP. With the new targeting system you could put one with some snipers at each of your defense lines to target spitters. But Executors will be much better.
  
• Rank D: Shocking Tower: They are quite good against the early waves but they won't be any good on the final wave as spitters will make short work of them. They don't have a good range and won't even kill Executives in one hit. Moreover they are almost useless against Chubbies and may take a hit or two from harpies before killing them (as they jump over walls). To top it all they are energy hungry.

• Rank S: Engineering Center: You need it to unlock the Titan research.
  
• Rank S: Titans: You need them to clear the map early. The earlier you clear the map, the more time you will have to boom your economy and prepare for the final wave.
  
• Rank A: Oil Platform: You will need Oil to produce and to maintain all the Engineering Center Units.
  
• Rank A: Executors: The best defense period. Spam them in the late game.
  
• Rank B: Advanced Farm: Quite energy intensive so it is best to build regular Farms before upgrading them. However more food means more economy so if you don't have any more grasslands, upgrading your existing farms may be of benefit. Be careful as they are costly to upgrade.
  
• Rank C: Advanced Quarry: Costly upkeep and energy hungry. It may be good to upgrade your Quarries though if you can't find any more ressources on the map and if you need Stone or Iron (for Titans).
  
• Rank D: Radar: Why would you need visibility when you killed all the zombies on the map?
  
• Rank D: Advanced Mill: Build regular Mills instead. If you are in need of space it's better to upgrade your quarries for more stone and build Power Plants. Advanced Mills have too steep an upkeep.
  
• Rank D: Blades Trap: Costly and not really useful, though more useful than Wooden Spikes.

Here is a ranking of all the units you can build in the game.
As for Research they are ranked from S to D.

Rank S: Rangers: The best unit by far. A good scout, it can cover distance very fast, is mostly silent and do not attract much zombies and is consistent in terms of damage. Against one runner, a ranger will only take one hit but with micromanagement and sufficient area to manoeuver, a ranger can kill anything but a harpy 1v1. Sufficiently massed it can deal with the early hordes quite easily. Their counter is the Harpy (59 damage/hit out of the 60HP of the ranger and the only zombie faster than the ranger), and the Spitter (as it has equivalent range and can 2 shots entire groups of rangers).
Moreover it is incredibly cheap (1 pop, 1 gold and no food upkeep, 120 gold, 2 Wood). They can reach veterancy which makes them more than twice as effective than a regular ranger.
They can also be used to lure away hordes.

Rank A: Titans: The most powerful unit. Considering the recent change with oil upkeep I chose not to include them as an S unit. Indeed they are quite costly (1 pop, 2000 gold, 40 gold upkeep, 2 food upkeep, 40 iron and 20 oil as well as 2 oil upkeep). They are however the best unit to clear the map when massed: awesome range, good damage and rate of fire as well as a very small AOE, quite fast. In terms of raw stats their only weakness is due to the animation which requires a small time to set up before being able to attack. They also generate a lot of noise but it is mostly useful it brings more zombies to the slaughter.

Rank B: Snipers: Their range and high damage allow them to be quite potent to deal with spitters and to kill zombies without attracting much attention. Indeed while they generate a lot of noise, most often they shoot from too far away to attract any infected.
They kill all zombies but the special infected (Harpies, Spitters and Chubbies) in one hit thanks to which they reach veterancy quite fast. Their veterancy makes them twice as good as they hit twice as fast. You can use them alone or in reinforcement with other units to deal with special infected (notalbly spitters) from far away. It is an excellent mid-game unit but quite costly with their food upkeep and 5 gold upkeep compared to the ranger.

Rank C: Soldiers: Stats-wise, the soldier is quite a potent unit. However it suffers from their very low range and high noise generation. They often end up being swamped by waves of attracted zombies. Their veteran level is quite powerful and a squad-sized group can really make wonders against non-special infected. They do struggle against spitters which outrange them by a huge margin. Their cost and upkeep both in food (1) and in gold (3) make them subpar compared to rangers.

Rank C: Thanatos: I haven't been able to play around Thanatos much. They are referred to as specialized melee units who can shoot missiles. As far as melee goes, they are bad. Incredibly bad and cannot even kill an infected in one hit (might have been a runner). They do shoot missiles though if they are not engaged in melee. They have a decent range, decent AOE and good damage but a very slow attack speed and a windup before their first shot when they get into position. They are also the slowest unit in the game. Massing them seems to be counter productive as they will tend to shoot the same target thus wasting most of their damage and AOE. They also cost Oil to upkeep but are not very expensive compared to Titans. They seem to be a very specialized unit, more suited for static defense than attack. They are quite potent when defending waves but I have found them underwhelming otherwise.

Rank D: Lucifers: While the Lucifer has high HP, it can't shoot over walls, it is very slow and sluggish and can damage allies. It does have decent damage and AOE but Executionners Zombies can and will get close; chipping down their health and slowly killing them. As an Engineering Center unit, they cannot reach veterancy. Their Oil upkeep and high costs simply crucify this unit as the worst unit in the game.