Death Strike is a variation of the Death Knight's Death Coil spell. The spell is used to damage an enemy non-Undead unit, and is best used in combination with Cold Strike. It is advisable to learn this spell first due to its low mana cost. During the early part of the game, use Death Strike to finish off footmen with low health. As with Death Coil, Death Strike can also be used to heal an allied Undead Hero or unit, making CattleBruiser a part-time healer in some games, but you can't heal yourself.