Halfling Heroine
I really hope Nyx comes back soon...I'd assumed with the dark elves' victory in the 12k Halloween event that we'd see his chaos being unleashed, but we've heard nothing since.
To be honest, even if Sen and Overseer regain their powers, I can't see them being able to challenge Nyx. Even when they were at full strength they were no match for Jack, who stripped them of their powers. And considering that Santa, Jack and EB were in fear of "Him" (presumed Nyx), I doubt the weaker Sen and Overseer would stand a chance.
It would have been very appropriate for Nyx to have unleashed his chaos during Apocalypsmas, what with the general theme of that event and all, but the time has long since passed.
Maybe this whole thing involving Jack, Santa, and the Easter Bunny all reconciling with one another may be leading up to a confrontation with Nyx. Individually, they wouldn't stand a chance, but together, they might. Of course, that would involve a level of foresight that I doubt the current plot writers have, but it'd be nice if they caught on to that.