The fic was focused on Loki and I think it was set after the Invasion of New York in an AU where Loki had been tortured by Thanos into a semblance of cooperation. Loki was imprisoned in Asgard as punishment, possibly without a trial, and he just wanted to die to get some peace becuase he refused to be imprisoned for the rest of his life. The only way he could manage that was by starving himself, but it would take several months to suceed. The author described Loki's refusal of food and his emotional state heart-wrenchingly realistically. I also remember that Frigga found out what was happening and tried to persuade him to eat by putting some fresh fruit from her garden on his plate, possibly wrapped in one of her hankerchiefs.
I'm 99.9% confident that Loki doesn't end up dying (major character death is usually a hard no from me). I also used to read pretty much exclusively frostiron, so it may have been Tony/Loki if the Avengers characters were involved. I feel like this was written by one of the major authors in the fandom and I'm probably going to feel really dumb for not remembering this. :)
Thanks in advance for any suggestions!