Some quick additions to Sans's part in holding Cas down, written here in case Sven needs to edit the full plan for whatever reason: Sans will be using the incantation he got from Rainer to summon 1d5 skeletons to help with getting her pinned down! He'll make extensive use of Misty Step here to keep her as disoriented as possible to which skeleton is him, along with keeping Digital Phantom up so she can't use her magic to track any skeleton in particular while he does the whole cover Cas in webbing thing. He can also try to hold her in place with Shape Water by just submerging her in five cubic feet of water.

If any other skeletons are still around for the rest of the plan, he'll keep using them, of course.