Deep north should be the “Lightning” themed biome in the game, not Frost.

Many of the biomes in this game have an elemental theme. Swamp contains almost everything poison related, Mountains contain almost everything frost related, and Ashlands will likely contain almost everything fire related.

The problem with making the Deep North feel unique is that most of the good ideas have already been taken by the Mountain. Wolves, Drakes, Fenrings or Golems would feel cheap and unoriginal rather than exciting, so none of these enemies are good options.

That's why I think it should instead be the "Lightning" biome. It could be full of dangerous lightning blizzards, shrines that steal lightning from Thor and corrupted lightning spirits.

It would be a dangerous wasteland of dark, stormy skies, crackling thunderfog and terrible, powerful spirits. The best comparison would be with midgard from God of war Ragnarok, after Fimbulwinter hits.

Lighting spirits would be the "Big scary" enemies of the biome. They would be big sentient thunderclouds of similar size to stone golems that drift along the ground. They could dash and shift around, and could summon a spectral Mjolnir to slam on the ground, creating a lightning explosion (similar to Yagluth's slam). They could also summon the spectral Mjolnir to quickly thrust it towards the player to knock them back, break their guard and electrocute them, but deal low damage.

There would be new lightning weapons too. We already have a lightning atgeir now which is a little problematic, but we could also have a lightning staff or magic that allows you to dash by turning into a thundercloud and dashing, which deals lightning damage to enemies.

Hopefully this sounds like a good idea to everyone. I think Lightning is extremely underutilised alongside Fire. Lightning is interesting because it still doesn't really have much of an effect, but doesn't damage over time like fire and poison.