Could the seneschal be the original Jack Frost, who is bitter that Odin came along and scooped up the Father Christmas power-tap while he was consolidating all his different masks (Kringle, Odin, St Nicholas, etc)?
Or Could he be the Krampus, 2nd in command to Kringle and actively pushing for a return to the darker days where Christmas was equal parts reward and punishment?
OR, as a slightly more out of the box option, could he be a norse entirely unrelated to either Christmas or the Fae, who doesnt particularly like either, and who has decided that the whole Afterlife in Valhala thing was wildly misrepresented in his youth?
Or, since Ravens can look like dark-haired supermodels, could he be Rudolph (Of the Red Nose, not of the Brown
)?