Soulstone

A Soulstone is a conjured item that a warlock can create beginning at level 18 with Create Soulstone spell that temporarily grants one player the power of self-resurrection. It is also a verb term for applying a Soulstone to a target, as in "to soulstone somebody."

Tips
Though really situational, it is actually possible to have both yourself and a target soulstoned at the same time. Make some time 15 minutes before your dungeon or raid and cast a soulstone on yourself; then log out. When you log back in 15 minutes later for your group, you will notice that the soulstone had its cooldown refreshed... but you didn't lose the buff! You can now cast a soulstone on your healer, and both of you will be able to self-resurrect.