The Chain and the Nazgul (minor TfW and DoM spoilers)

[Summerhawk]

Another option I considered for replacing the Gibbet King was using the Sorceress at the Demon's Tower in southern Mirkwood. It keeps the aspect of dark magic while still removing the 'wraith-like' Gibbet King. For mine, I liked Mormog because his nature hints at the growing reach of Mordor (even though our characters are largely ignorant of that), and my players enjoy it when the wider world reaches into the smaller world of the campaign.

That is good advice about the various magical aspects of the coming adventures. I may use Feredrun (which I had not considered before; it's a good idea), or perhaps adjust Mormog to give him a little bit of sorcery he's learned either in Mordor or from one of the Nine. I will probably have Mormog personally present at the Celduin battle, but hanging back and retreating if the battle turns against him.