Multi-“body” monster(s).
Several “shells” appear in several corners. At start only one (or maybe zero) is animated. When animated one is destroyed “essence” flys from destroyed one into another “shell”. Psi is absorbed only after destroying last shell. “Shells” can be destroyed(sometimes) even if not animated.
Variant - “essence” acts as amplifier for usual monster (only for certain type). Possible to make map where “essence” can posses into any monster, even for different types randomly.
“Support fire” monsters - extremely slow, wide range range attack,(possible) multi-target, high hp, possible magic attack.
“Tower” monster - at some check-points this monster transform self into immobile “tower” with range attack for some time.
Transformation monster - when entering another map area or just at another 20% of it’s path, or entering the corridor with another color - transforms into another type of monster - or into another form - this form is constant while at this stage.
“Medusa” - turns units into “stone” (it’s a spirit!) for some time. “Stoned” unit cannot act and cannot be unsummoned. Possibly “stoned” ones cannot be damaged.