"A long time ago, a shapeshifter named Thjazi kidnapped one of my relatives, Iðunn, who grows apples of eternal youth. Thjazi kept her prisoner and stole her apples, so the rest of us would grow old while he and his daughter lived forever. But most of my family searched for her - we searched in towns and around farms, we searched the skies, we asked for help searching the sea, and eventually we found someone who had helped to kidnap her and knew where Thjazi was keeping her. We threatened him into helping us rescue her - we sent him off to shrink her with magic and fly her home to Asgard.
Of course, we knew Thjazi would fly after him, so we laid a trap. We laid out all the fuel we needed for a huge fire right by the gate, all plane shavings and stuff that would catch fast. The wall doesn't really let you fly in over it, so Iðunn came in flying just above it and Thjazi had no choice but to follow her or turn back. We lit the fire just as Iðunn got past it and it blazed up fast enough to set Thjazi's feathers on fire. So that brought him to the ground.
Even so, he was still a dangerous shapeshifter - but he was on fire and surprised so many of us were waiting for him. We won." People from the area this place is modeled after don't usually like more gory details than that these days.
"His daughter came to us afterward. For revenge. We made a monument to Thjazi and did a couple of other things for her and she forgave us."