Lichborne

Lichborne is a death knight ability that allows you to draw upon unholy energy to become undead for 10 seconds. While undead, you are immune to charm, fear, and sleep effects.

This ability allows a death knight to self-heal using Death Coil. It also makes the death knight susceptible to abilities able to target Undead mobs, such as Shackle, and on the other hand, it makes abilities which can only be cast on humanoids, like Sap, unable to be cast on the death knight. Removing Lichborne does not remove CCs.

Lichborne is similar to the Undead racial ability Will of the Forsaken.