Update:
Galarian Slowking is now available in the Crown Tundra. It released on October 22nd, 2020.
In Galar, Slowking has a Poison/Psychic-type regional form, introduced in Pokémon Sword and Shield's 1.3.0 patch. It evolves from Galarian Slowpoke when exposed to a Galarica Wreath. It is one of Galarian Slowpoke's final forms, the other being Galarian Slowbro.
It looks like this:
Source
As Nintendo has mentioned, Galarian Slowking will appear in the Crown Tundra in Autumn 2020. It's unknown as to what Galarian Slowking will look like, and how to evolve Slowpoke into this, but it's coming out.
