Undead Champions are powerful, dead Chaos Warriors, brought back to life by a Necromancer or a Liche to serve him. They are extremely faithful to the Sorcerer that raised them, and will serve them faithfully.
Undead Champions are Fearsome Monsters. They are so horrible looking that they cause terror into all their enemies. Anytime a Hero starts his turn in the same room as one of these monsters, he must make a 'Fear' roll at the start of his turn. The Hero rolls 1 red die, and on a roll of 5-6 he has become afraid and must move as far as possible from the monster, even if it means leaving the room. The Hero may not make any attack that turn, even against another monster, but can defend. If a Hero enters a room with a Fearsome Monster during his movement turn, he must make a Fear roll immediately. The fear only lasts one turn, but the Hero must make a fear roll every turn he is in the same room as a Fearsome Monster.
You can download an Undead Champion monster card here. You can use it for the Undead Champion's stats.
The cheapest way to play an Undead Warrior is to use a Chaos Warrior figure.