The Dying Earth uses a Resistance attribute. (But attributes in that game are different from, say, a D&D save - you can keep spending down your attribute pool to take rerolls, until your pool is empty. Each attribute has its own fiction-based criteria for refreshing the pool.)It's funny how some games do feel the need to have a hard rule to keep players roleplaying appropriately. Vampire the Masquerade can saddle you with a weakness (or you can saddle yourself with a Flaw) that enforces behavior like this. Ideally, sure, the player should roleplay these traits, but if one can resist the urge to press a red, shiny, candy-like button, when is it appropriate to do so?
A person with an obsession isn't necessarily ruled by it 24-7; they may have the willpower to resist or control their urges. If we leave this entirely up to the player, then when do you cry foul?
Let's assume we have a kleptomaniac. Do we cry foul if they are always stealing things? "I just have poor impulse control!"
Do we cry foul if they only steal irrelevant things? "Come on, I'm not suicidal, I'm not going to pickpocket Emirikol the Chaotic, he's been known to magic missile people that look at him funny!"
Rather than avoid any arguments about when it is or is not "kosher" to resist one's urges, or try to police someone's roleplay, perhaps a die roll to resist is the most fair solution.
What obsession?Reading Permeton's log from Torchbearer, I got similar wibes, particularily when Fea-bella read the cursed summoning runes. Then she made a Will check to stop reading. This is where I frown. In a narrative game, it ought to be Fea-bella's player who decides how far to play her obsession.
Fea-bella was able to read the runes without taking a turn, in virtue of her Instinct. This is somewhat analogous to the way a 5e rogue/thief can perform various actions as bonus rather than normal actions (Hiding, Sleight of Hand, etc) - I've never heard these called "obsessions" before, as opposed to say "knacks" or "skill tricks". The Will test was to avoid the ensorcelled runes that compel someone to read them. I lifted the trap from an ICE MERP module - in that system it will have been a Resistance Roll, probably based on either EM or PR. In classic D&D it would be a save vs Spells.
Fea-bella's Belief is the result of being cursed by a possessed Elfstone - her Belief is that the stone must be protected. Unfortunately it is currently lost - stolen! Fea-bella's player chose to act on this Belief by trying to bend the seeing throne to her will. The failure to do so is what led to her falling unconscious and hence being dragged off by aptr-gangrs.