How do you resurrect Allies?

When you are playing with other players and they die, there is a "gravestone" (shiny blue cross) you can click on to resurrect them

Casting resurrection usually takes a few seconds, and getting hit interrupts it, so you'll want to be sure the area is clear before you click to resurrect your ally.

Everyone has the ability to resurrect their allies, however once the dead player clicks [Respawn at Last Checkpoint], the option to resurrect them is gone.

Once you finish casting, the dead player gets the option to accept your resurrection, or they can still choose to respawn at the last checkpoint.