A collective mind partly formed from the re-absorbed essence of the Operatic warlord who once cast War Crime.
In its addendum to the War Crime description, The AI shares an additional fun fact: the Operatic Collective warlord who cast the spell during The Mantid Massacre supposedly had to go for an identity reset after his crawl, and part of his essence was eventually re-absorbed and formed into the Hortense Leadership Unit. The AI would like to think that's why Hortense has a twitch to him.
The AI adds that collective minds should really have learned by now how to peel off their own impurities — otherwise, it says, you're just wallowing in used bath water. Carl believes this whole last part of the description appeared for no one other than himself, and it gave him a terrible, foreboding feeling about the spell.
A collective mind whose twitch the AI attributes to a war criminal's leftover essence.