There is obviously going to be some important use for these coins. I agree that more than likely, we will be going to Avernus, it would be cool if we had to use them to "buy back" a companions soul. Although what would also be cool, is if there were "bonus" treasure areas in Avernus, maybe a maze, or dungeon, that will be opened by the coins, where you can go to get gear or treasure. They did a similar thing in DOS 2, where you could use soul jars to access areas in a graveyard or some ruins or something (can't quite remember).
