The new Imps models are funny
But after a few seconds of trying it out
(maybe/probably this is discussed in the stage 10 thread, but I didn't really follow that one. if so, sorry):
The zombies and lich are moving towards/attacking the target while the animation of them comming out of the ground is still ongoing.
The imp(5) dies after 1 attack.
The monsters do one extra attack after they defeat a summon.