If anything, the rewards for siding with evil should be greater, at least at the beginning. Most Evil people don't do evil deeds for the pleasure they get from murdering/stealing/etc, but instead because they are selfish, and doing those deeds benefit them more.
There's the common trope that doing Good will not be that rewarding in the beginning, but will eventually put you in a very good place. Evil, however, is rewarding up-front, but you'll eventually get what's coming to you.
True, that’s a common trope but I don’t think it needs to be that way, and in fact it might be fun to turn it on its head
! I think an unscrupulous, selfish character with no regard for life already has a good reason for going with Minthara given that the cult seems a potentially better lead for finding out what’s going on with the tadpole - which as a threat to life is surely higher priority than good loot right now - than Halsin and certainly than the Tieflings. Or it could be a good reason if clearly articulated and recognised by the game.
