Yo, he ain't technically an incarnation. While not all Incarnations are alike, or even share the same physical properties, the one thing in common about them is that they are literally a mass of whatever they are the incarnation of, that has, some way or another, gained sentience, a form, and possibly life(a incarnation doesn't have to technically be alive, in a matter of speaking).
Whatever he would be, he wouldn't really be an incarnation considering the Negion needed a catalyst, and mind that even if he were a Incarnation, he wouldn't be close as powerful as a embodiment.
Also, I find it interesting that he would have something containing the embodiment of fire...How would it get in there in the first place, and whats to make it actually obey whatever orders are given to it?