Might and Magic Edit
Most of the games have undead foes that the party can face. There are usually spells that cannot affect undead monsters, and others that can only affect undead monsters. For example, the Fear spell from Might and Magic IX has no effect on undead monsters, while the Turn Undead spell has no effect on living monsters.
Heroes of Might and Magic Edit
In the Heroes series, undead are connected to the Necropolis faction. Most or all Necropolis creatures are undead, and most or all undead are Necropolis creatures. Undead creatures are immune to the effects of morale, both positive and negative.