Chaos is not playable yet, they will be in the future.

I've been trying some workarounds. It is possible to join the Faction in the Brass Keep. You can conquer Castles and Cities, which also give you the opportunity to recruit there, instead of recruiting prisoners from the Chaosgate. But the Factionleader always wins the votes. What you could try:

1. Skill Rougery
2. Get your Clan to Tier 2
3. Join the Brass Keep
4. Rise your Reputation with all the other Members of the Brass Keep (and farm Influence)
5. Lure the Leader into a Battle he can't win
6. Follow the Enemy and hope he puts the leader into a Prison
7. Sneak into the City/Castle, bribe the Guards and start a Prisonbreak
8. During the Prisonbreak, you'll have to kill the Leader
9. Start a vote for the new Leadership

I've tried it, but couldn't get over step 7. (EDIT: I'm not sure if it is possible to bribe the Guards from a hostile Faction tbh).

The best way is to play as Necromancer or Vampire, because you can use the Undead to fill up the Garrisons and Armies (= Influence Income). Every Faction will be at war with you.

Thx for the informations

AI cant die in battle though?

Well... that's worth a try. Didn't came to my mind XD

But in Vanilla it works 100% the way i described it. Without RNG. I will give it another try.

EDIT: I don't think it will work, because of the Campaign Options -> Hero Deaths in Combat aka Birth and Death Module