[Squirrelloid]

They do receive the sacred flag (if they didn't already have it), so at the very least their upkeep should be reduced like any other sacred.

And most of the time those prophets will be your freespawn commander units - now, its hard to tell given how much freespawn you can get in a turn, but i'd guess at least the aquatic ones don't cost any upkeep normally (deep one looking ones) because you can't otherwise buy said unit. Testing this would be rather hard, however, unless someone who has modded the game knows if the freespawn commander has a cost associated. Anyway, if he's free normally, he's still free when he's a prophet.