Given what we just saw happen to Lawless's character, is it possible that the Guest House alien isn't an alien at all, but a human transformed and possibly killed by 084? That could mean that Sif was on the money when she said the Kree hadn't visited Earth (assuming the artifact is Kree).
Perhaps, but she only mentioned the Kree is passing as one of a number of species with blue skin, before giving a blanket statement that there had been no visitors to Earth (implicitly since the frost giants?)
Plus of course...
...we know for a fact that Yondu (a Centaurian with blue skin no less) and a ship full of various aliens visited Earth briefly in 1988. Then of course there was who/whatever Quill's father was at least 8 years before that.

That aside, it seems as though the transformation turns human bodies solid, grey, almost stone-like (one person was seen as such in the prologue.) It didn't turn them blue and that body was clearly still flesh and blood, with a number of injuries not consistent with what we saw that thing do.