Originally Posted by
Sutekh
It would be a neat way to build up Chthon as a serious foe. He's supposed to be one of the eldest demon-god-thingies, on a level with Thor's mom, Gaea, fellow elder-demon-god-thingie Set, or pantheon heads like Odin or Zeus, but has generally been confined and limited to working through intermediaries, like a possessed Modred the Mystic, or a possessed Wanda.
I think it could also elevate Wanda a bit, to have a foe that's close to Galactus or Mephisto-class, more than a match for even big-hitter Avengers like Thor, sort of the 'Dormammu' to her 'Dr. Strange.' Even if she's not going to get into a fist-fight with him, he could still send cultists, lesser demons or possessed flunkies to give her trouble, and she might be integral to breaking up various rites meant to draw power from him (and so increase his power in the world, and hasten his eventual return, and perhaps weaken the users to make them more susceptible to his influence?). That would be neat. Lesser mystical foes start using an invocation called 'Clutches of Chthon' to cause a cage of stone bars / pillars prisons to rise up and possibly begin closing in and crushing enemies, drawing power from him to fuel the invocation (the way Strange used to with the Winds of Watoomb or Crimson Bands of Cytorrak), but the hidden cost is that the more you draw his power into yourself, the more he's slithering inside you...
(All sorts of evil entities could fuel invocations, that we'd never see someone like Dr. Strange using, but evil spellcasters could call upon the Dread Gaze of Dormammu or the Serpents of Set or the Tinders of Tolomaq or the Dagger of D'Spayre or Tiboro's Transport or the Lies of Loki or conjure the Hordes of Hela. Tons of options!)