[Taqwus]

It's already fairly easy to bamboozle the AI with bad gifts -- for instance, Bane Venom Charms or Lycanthropos Amulets, as the AI has a tendency to put these items on its pretender or HoFers. BVC in particular diseases both troops and population, making it a cheap double-whammy, and since it's not cursed the risk of blowback from picking it up is greatly reduced.

It might also take some doing to have it realize who's the likely suspect nailing it with anonymous magical attacks, thus breaking any "treaty".