Despite what various Ars magica sourcebooks might tell you there is actually a lot more than frozen wasteland and hostile heathens to find in scandinavia in 1220.
Denmark was formally christianized in 975 and is in 1220 very much a christian kingdom involved in the larger political landscape of mainland europe. Even going on "crusade" in Estonia in 1220.
Norway has even had its own archdiocese since 1154. There is a lot more to look up but these are just my own two cherrypicked examples.
In a way scandinavia is simply ripe for hermetic conquest. Scandinavian economies are deeply involved in maritime trade with amber, walrus ivory and fish to name a few things. They are also happy consumers of southern luxury goods, like wine and silk. There are trade routes to iceland and greenland for the transport of these goods.
Thus there is ample opportunity to set up a covenant economy, based on the import/export of goods. Especially in Norway where farming is hard it should be possible to set up a thriving farming economy for a covenant by employing magic to mitigate the harsh climatic conditions.
A really good reason to go is simply to set up shop somewhere that is free of competition. If you are the first to go you also get to claim dibs on a larger amount of the magical resources, you can pick the best auras/regiones to settle in, claim all the vis sites, take the best familiars, ally with the strongest magical (Magical/Faerie) beings, ally with/influence the strongest mundanes etc.
Given the lack of hermetic covenants there should also lots of available magic resources.
Auras, regiones, vis sites, magical monsters, beasts of virtue.
Norway in particular is full of majestic natural wonders:
a predictable(tidal) and massive whirlpool, the Aurora, fantastic maritime beasts, majestic mountain views, a diverse fauna, rock carvings etc.
In many places in scandinavia (I know this is true of denmark since I live there, but it believe it to be the case for Norway and Sweden too), you can hardly turn a stone without finding evidence of stone age and bronze age settlements. The bogs are full of bodies, and especially votive objects. There are thousands of burial mounds in different styles ranging from early neolitihic to late viking age, ending with the christianization. You might even be able to find people who can remember the last burial mound constructions. These mounds are sometimes full of treasure too, especially the ones from the bronze age.
Then there are the Sami. In norse folklore the sami are thought of as great magicians. That is a really good opportunity for introducing all sorts of interesting magic. Perhaps they have access to some magical knowledge that could be integrated into hermetic magic? maybe their reputation as great sorcerers is caused by an unusually high amount of Gifted people among them? They are an ideal vehicle for introducing some exotic magic that you like.