Decided to play around a bit with a hex editor in order to test the behavior of a certain ability you can get late in the game. Those who''ve played far enough in the game will remember reaching a point in the game where the gods die (which may make the religion skills useless or take them away, not sure because I haven't played that far or tried to hack in the trigger for that), but then later you are given the opportunity to convert to the Ancient One's religion. Now, I've been wondering what happens if you start worshiping the Ancient One, and then use the pray or worship command, so I created a Cleric and used a hex editor to change their deity to Ancient.

Outside of battle, this doesn't seem to happen, and doing so seems to make it impossible for this to work during battle later.

During battle, it appears that you'll get a random spell to be cast. The spell's name is displayed, and you're given the chance to choose the target, and then the spell is cast at a high power level. I don't know the full list of the spell, but on the two successful uses I've had I've seen Summon and Tempest. Tempest was strong enough to kill the two affected enemies in one hit, though I should point out that the enemies I tested on were early game enemies.

Summon, on the other hand, seems to be affected by a bug. When I got the effect, I tried to summon a Spirit Elemental, but then the game told me that I don't have enough SP. Thing is, since this is the result of prayer rather than a normally cast spell, this shouldn't require any SP from the player character, but yet it does, and I consider that to be a bug.

(Wondering how items that cast Illusion or Summon behave.)

In any case, many players didn't see the point of converting to the Ancient One's religion, and now, if you're reading this, you know what it actually gets you.