Me and a player (a non-council wizard) are toying with the idea of having a shade of Merlin ride around in his head (a small part, one of many Merlin left laying around after his death, at least in our campaign). I'd like to stat this as a Demonic Co-Pilot, but I'm not sure what sorts of Demon's Agendas I can Compel him on with such an ultimately benevolent (as far as we know) being.
I thought of Fate itself, as Merlin intentionally submitted himself to entrapment and death at the hands of Nimue in The Once and Future King, but that doesn't quite seem like enough. A few more minor agendas to add onto that, or one big one would really help.
All we know of him (in canon) so far is that he was the keeper of Excaliber/Amoracchius and he created a prison for demons. That's more or less in line with the types of thing the party goes for, anyway, so it doesn't seem like it makes for strong Compels.
So, ideas?