avengers_search | Odin makes Tony immortal by throwing something

A long time ago I read a Loki/Tony one where after some time Tony is granted immortality but Tony does not accept, but s he is so good for Loki Odin just throws something at him in midair and he gets immortal. I know it is vague and I do not know if it ever got finished or not as there was no way in to Subscribe for updates at that time. I'm searching for it for a long time but there are so many stories out there and it is driving me crazy. LOL.
Can someone help? Other recs in that style are also appreciated. I love to read.