I've never encountered this spell in previous games, but there is a Kraxis spell Broken Loyalties.

A quick search indicates this was changed from having mana cost to having gold cost. So in other games, either the AI chose not to use it, or couldn't afford it.

It appears the game (with this faction present) might be completely broken as a result - or have I missed something?

So I'm on Season 75, have never met Kraxis (who is a minor faction in terms of power rating), then all of a sudden he owns one of my cities. And he also does this to some of my allies' cities too - possibly in the same turn. Presumably, as I've not seen his scouts, he has used a spell to scout me out, or has an econ treaty with a neighbour.

Because mana is not required, and AI factions start with 50,000 gold (I play with all settings on insane, to reduce throwaway games which have become a pushover by mid-game and all my time/strategy investment is wasted), this spell is incredibly cheap.

So at season 75, even with the expected AI rush-buying every building they can, he still has 38k in the bank. There are less than 38 cities on the map (at a guess, I've barely explored a third of it). Does anyone see a problem here? What on earth were the devs thinking making this so darn cheap?

I'm particularly miffed, as I was 2 turns away from building the Great Mill, which was quite expensive - I lose all my population, production progress, and numerous buildings. I could accept this and recapture and rebuild were this an expensive spell he is likely never to afford again, and not against someone he has never met and has no particular quarrel with. But if I take the city back, am I just going to put all this effort back in only to have my buildings / production progress and all my population obliterated over and over again?

Sounds like Kraxis is a broken faction for now - is this a known issue, and are the devs dealing with it?

Or are there some sort of hidden checks and balances to prevent him recasting the spell on the same city/faction until his gold runs out?

This used to be such a fun game. I decided to fire it up after a year or so as I got the new DLC packs - and was really getting into my game, and had a lot invested in it - so this is very frustrating. I'm faced with having to start all over without this faction present or go play something else.