How to find Misa
In order to fight Freya, you have to get an item that prevents her from freezing the whole party. Without that item, it is not possible to kill her, and while you can get it from the npc Jinia (without doing the quests), completing the Freya quests will give you 5 of these and then access to the permanent core. Out of all Freya quests, only one is not necessary to do (An Ice Merchant’s Dream) but it still gives an item (Silver Hemocyte) to access the Ice Fairy Sirra raidboss.
I won’t write a guide for the quests here, as enough of them exist online. What I will tell you is how to find the mystery npc Misa from the first quest “The Other Side of Truth”.
When you teleport to Ice Merchant Cabin, you pass Rafforty and continue on the path. When there is a path to the left you choose that and continue to walk on the path. This path leads west to a bridge. BEFORE the bridge, and I mean right before the bridge (do not cross the water) you turn right and start to walk on the snow along the lake line. Continue to walk on the right side and at some point the hill on your right gives way to the right and reveals the Frost Lake. Misa appears only at night (use the command /time) on one of these pieces of floating ice.
Walk by the npc and take the path that unfolds before you.
This is the path. Turn LEFT when you are given the choice.
Keep walking until you find the bridge.
BEFORE the bridge turn right.
At some point the mountain allows you to go to the right. You have found the Frost Lake!