It's a bird, it's a plane, it's a BIRDOPLANE ZEROPEDIA! ːcool_seagullː
Every time you kill/lose a unit, or cast a spell, it will be added to this magnificient tome of ancient knowledge.
Sorry guys, I wasn't able to add every unit/spell you already killed/casted before this update. But some of them will be (the game will count every suitable quest and every achievement to fill the book)

Also, fixed a wierd bug in a combination of Confuse/control spells + Spawn after death perk