Reima’s Shards

Could you create something similar to the Kirishimok abilities from the first expansion?

As I mentioned, if you're interested in this concept, I can add it, but it won't be appropriate everywhere, as many events may be focused on combat experience, and there's not much point in tempting ordinary demons and monsters.

Is it mandatory to be part of the faction that is chosen? Or can you play solo?

You can choose any origin, but the starting storyline is based on the chosen faction.