Paladin accidentally connected to evil god and doesn't know it!

[Arbane]

Only advice I've got is to not do the whole "trick the Paladin into falling without warning" thing, unless the player is okay with it.

What kind of carebear nonsense is this? If the player didn't want their character concept involuntarily warped beyond regonition, they wouldn't be in a game. The player knew perfectly well what they were getting into, as the only reason to play Paladins is so they can fall. The GM is the player's eyes and ears, so they are totally entitled to feel smugly superior when they 'outwit' the players by lying to them constantly.