Giving permanent buffs to your cards is intentional, otherwise you'd have two souls to take down one enemy. Optimally you use selfless soul to buff up your souls in the early rounds and then either change it for a tortured/malicious soul or buff the enemies for extra score if your souls are powerful enough.
There is no lose state in this game, I wanted to make a chill card game without stress of losing. If the player wants to skip through every round and get a score of 0, they can. Basically, every player can decide their own win and lose state.
I'm glad you enjoyed the game and thank you for playing.