Angel of Insanity:
Hell's Invasion has left you a bit.... touched in the head.
This is a variation upon the Angel of Hallucinations, but instead of weird bizarro wacky things, instead, all items and monsters have random icons, so it is quite plausible that a Former Human could look like an Archvile until he shot his pistol at you. Similarly, on maps with large quantities of lava/acid, certain tiles will be marked as dangerous when they are not, and certain tiles that ARE dangerous will appear normal until you step on them. Levers, however, will remain normal. The effect message, however, will be blatantly false, and will appear to reflect the false message until you actually test it, revealing the effect to be false.
A bit of a note to make things easier: Enemies will be revealed as their true selves once they fire. Equippable and usable items will be revealed when you get within two squares of aforementioned item. Barrels will remain hidden as their insane visions at all times. Each rank increase of Intuition would increase this "Detection" range.
This isn't the weird goofy hallucination stuff, this is dead serious hallucination stuff.
The Advantages? Weeeell, you could overestimate an enemy, and overestimation of a foe NEVER hurts.
The Disadvantages? You could look at a barrel right next to you and think it's a Former Human, just ready to shoot at you.