AI cheating on single-player maps.

I once encountered a similar situation on an M-map from the AB set. The enemy had either a Portal or Dimension Door, but I didn't see anything in the guilds or when capturing artifacts. However, I didn't think much of it at the time and chalked it up to my own poor skill (I've dealt with worse AI glitches!). But I don't remember anything like that happening since. Now I'll keep in mind that the AI can cheat, not just be stupid.