In every campaign I have ever played, the only guild I have ever seen in any enemy city has been the thieves guild.
However, in my current game, I have modded the campaign such that every faction starts with a fully upgraded citadel and huge city, in order to make the AI build some more interesting armies (it actually makes battles quite challenging, the AI builds some nice stacks of e.g. Spanish dragoons, chivalric knights etc.) One result of this seems to be that the AI actually gets some more interesting guilds. So far I have conquered the Iberian peninsular as the Moors, and have yet to encounter a single thieves guild; in fact, the enemy cities seem to get all sorts of weird guilds like alchemists' and horse breeders' guilds which I never even get unless I'm specifically aiming for them. Plus the castles all seem to have either a crusading order or a swordsmith's guild. I found this quite interesting since I had assumed that the AI would always end up with thieves guilds rather than anything else.
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