avalon spell vendor give the recipe, get 10 rata tc and the other reagents and you can craft it as a permanent spell. grizzleheim pack with luck (give tc and the spell itself but rare drop.
There are 2 ways to obtain the spell that I know of. Firstly through being lucky with whichever pack drops it. The second option is crafting the spell which is rather hard as you need Amber and Ratatoskr's Spin, plus all the other ingredients. If I recall correctly the recipe can be bought from Grady in Avalon.
I've come across life wizards having the Ratatoskr's Spin spell, was wondering how to obtain it without it being just a treasure card?
Unfortunately, this spell must be crafted. It is unfortunate that it is so difficult for life and death wizards to get a 4 pip aoe compared to other schools! It has made me play my life wizard less.