I’m looking for a certain fic involving Loki and his children
The Avengers (possibly FrostIron) help Loki travel through the realms to recover his children.
Sleipnir is a foal and can transport people thought the branches of Yggdrasil. They sneak him out of Odin’s stables from Asgard.
Fenrir is trapped in Jötunheim bound by chains thatif broken will cause Ragnorok. Tony Stark melts the ice that are holding the chains, thus freeing Fenrir.
They all return and live in the Avengers tower