It was on Ao3 and Tony was an angel/cherub. There were other people from the MCU that were angel/cherubs as well and they got assigned to other characters from the MCU. Tony was assigned to Steve and they were supposed to help their humans out. After awhile the cherubs would get bigger but Tony stayed small for a really long time. Longer than any of the others.
That's pretty much all I remember and I'm not even sure if it's all right. Any help would be appreciated. Thanks in advance!