Those mechanical effects can be removed by Lesser Restoration (blindness, deafness) and Greater Restoration (exhaustion). In addition, a Theurg can use Purging Fire to get rid of permanent Corruption. If he has a Theurg friend that can cast Protection from Energy and heal him, he doesn't even care about the fire damage!A goodly number of the marks of Corruption have mechanical effects: Exhaustion (which will kill the character eventually), blindness, deafness, and effects on social encounters {which still can happen in the forest - Queen's Rangers, barbarians, goblins, etc.), plus the chance to get permanent Corruption, which will eventually turn you into an abomination. We're in the process of taking a second look at everything but we've had that decision play out in playtesting and not end well for the character.I just realized that in RoS, there is no upper limit to Corruption. You can keep adding to it waaaay past your threshold, you just keep rolling on the Corruption marks. RoS does not have this rule found in Symbaroum: "The character turns into an abomination if its Total Corruption (temporary+permanent) reaches or exceeds its Resolute value."
What if a player character just doesn't care what side effects it gets from Corruption? As a GM, I can always make the world react to that, but in the middle of the forest, who cares that you crave raw meat and stink of death? I would like a rule similar to the one in Symbaroum, just to keep the players minding their total Corruption.
Once Theurgs reach 9th level, there won't be much to stop them from casting all day long.