Captain America #290, by JM DeMatteis, Ron Frenz and Steve Leialoha with a cover by John Byrne from 1983 has the first appearance of the character Mother Superior. Who is revealed as the daughter of the Red Skull, now known as Sin, and the star of the upcoming Fear Itself comic from Marvel.
Currently, there is what’s known as “activity” on this book. People are mopping up all available copies on eBay for anything up to $4, when there hadn’t been a sale of this individual comic in eBay for months.
Might be worth looking, as I did, in your longboxes to find a copy?