Neverwinter Nights 2’s expansion — Mask of the Betrayer — is frequently cited as Obsidian’s finest narrative work before Pillars of Eternity. The protagonist wakes in a barrow with a curse: the Spirit Eater, a hunger for souls that grows throughout the game and must be managed through dialogue choices that involve consuming or resisting spirit energy.
The Hunger is not metaphorical. It is a literal mechanic where the protagonist’s alignment and available options change based on how much they have fed the curse. Players who consumed aggressively had more power but fewer narrative options; players who resisted had the opposite.
The game’s final choice — whether to consume the god Akachi’s spirit or free it — determines an ending that reflects the entire run’s Spirit Eater management. Players who resisted the hunger throughout receive an ending where the protagonist masters the curse; players who fed it receive an ending where they are mastered by it.
Obsidian built a mechanic that tracked the player’s ethical decisions across 30 hours and produced an ending calibrated to the accumulated choices rather than a final decision alone. Mask of the Betrayer remains unusual in that its ending is determined by long-term resource management rather than a binary final choice.

Currently on my first run and now I have to go back and look for this. Worth the detour.
Found this by accident on my third run. Came here to understand what I was actually looking at. Great write-up.