"You feel your perception being magically altered."
A state that allows you to detect warm-blooded creatures around you, even if they are invisible or behind a wall.
With the addition of the fire system, you can now detect burning objects and monsters as well.
Can be gained via ring of infravision, or as an intrinsic ability possessed by certain monsters.
If you have made yourself invisible, infravision will allow you to see yourself once more.
"You feel your perception returning to normal."