If you are attempting to ascend on the altar of a god to whom you permanently converted alignment, you sense a conflict between that god and your original god. There is a 1/3 chance that the original god prevails; in this case you feel their power increase and their voice booms: “You were destined from birth to deliver the amulet to me!” This forcibly converts you (but not the high altar) back to your original alignment. You retain the Amulet of Yendor, and now must make your way to your original god’s altar in order to ascend properly.

Non-Infidels can permanently convert to Moloch if they find one of his altars, effectively becoming a weaker Infidel, but they then somehow have to play out the rest of the game as an Infidel, which means finding the Idol of Moloch and getting to the Astral Plane with it.

If the player permanently converts their alignment, they get Wizard-style harassment for the rest of the game by their original god. (This stacks with the Wizard’s harassment; after killing the player will begin to be double-harassed.) The only difference between god and Wizard harassment is that the Wizard won’t spawn. All the other effects remain the same.

Permanent alignment conversion prevents you from receiving any more protection by donating to a priest ever again.

Crowning makes it impossible to change alignment ever again. You can neither permanently convert at an altar or put on a helm of opposite alignment after you have been crowned.

The helm of opposite alignment has no effect on neutrals (except autocursing). Alternatively, some helms may turn lawful and chaotic characters neutral.

Make permaconverting harder to do by accident, since confusing the actions of rededicating an altar and rededicating yourself seems unlikely. Maybe make it happen if you sacrifice or pray on a crossaligned altar while confused.