The spell has several limitations. It can only be used on players that died within certain range of the caster and will affect them only after 10 seconds pass from the moment of their death. Furthermore, while it can always be used on allies, it can only be used on unallied players only if both the caster and the target player are friendly.
A downed player can avoid being revived by using makecamp command before the spell is cast.
A Magic Skill of level 20 is required to use it.