You may see that snake is covered in blood, with a very long horn on his head.
There are some reasons for it, but the main ones are:

1) You have killed a lot of enemies from the beginning of the game.
(killing enemies in a bad way like burn them with fire or kill injured ones, will increase your demon points much higher).

2) You have completed the mission "shining lights, even in death"
because killing all staff members will highly increases your demon points.

3) You have developed a nuclear bomb (the most effective way).


There are a lot of ways to do this like glitching, bugs, modding and etc.
But you can do this in a normal and fast way.

So, lets begin:

As I said, your actions in the game will affect your demon points. There is a long list of this actions if you check youtube or websites, but we just need these two:

-120 – Fulton extract a child
-240 – Extract a child via helicopter

Open you idroid and select "white mamba" mission. bring the below items with yourself:

D dog (DD) as buddy
A Jeep
Sleeping gas
A dart pistol

1) So, start the mission. Put every child soldier that you see to sleep.
(You can also stun them but it last shorter and they will wake up soon).


2) Pick them up and gather everyone near their boss cabin.
(Be careful, if it is raining, the holes in the ground will be full of water and it can drown the kids. So you will fail the mission).
(You can use jeeps in order to gather the kids faster and they cant wake up and escape).


3) When you are done, fight with their boss (Defeat him as fast as you can).


4) A chopper will be there to pick you up. First put every children into the chopper and then their boss (This is very important).

5) Complete the mission with the steps 1 to 4 again and again until you get rid of the demon snake.

Good luck.
And Im sry for my bad English :D