[Ewierl]

I think their purpose is that, for most nations, they are the only summonable priests. If you're doing teleport strikes and attacking with SCs and mages behind enemy lines, you may not have any way to establish a dominion/temple foothold in enemy lands. If you're someone like MA Man or Bandar Log, with all your mages as sacred non-priests, you're going to have lots of trouble recruiting mages in a newly-captured fortress. Telestic Animation, however, lets you bootstrap from Astral magic into priesthood.