When a hero with the Necromancy ability deals the killing blow to a small (no bigger than one space), normal, unnamed monster (and it stays dead, in the event of Undying or other such effects) he may choose to animate the monster. The monster stays on the board and is returned to full health, but falls under the control of the hero. A hero cannot control more than one monster at a time, but may choose to let a monster under his control die in order to animate a new one.
An animated monster moves just after the controlling hero’s turn ends. The monster activates just like it does for the overlord player, save that it is under the direction of the controlling hero. However, after the monster completes its activation, the controlling hero must roll one power die. If he rolls anything other than a power enhancement, the animated monster falls apart and is killed.