The elemental and its host merge together. Its almost exactly like the Malevolence ability of the Ghost.- Exactly where does the subject go, once it has been inhabited?
I thought of allowing them to be summoned, but then you could just get them to use Hypercognition for you and that'd be a bit unbalanced.- Can you summon 'em? Or make 'em?
And no, you can't make them, though I'm sure someone could develop a PrC that lets you do something like that.