Sullivan (Labyrinths)'s Links
Though at first wary about Aislind's nature as a Seraph and what that means for someone like him, Sully eventually reveals to Aislind that he's been supporting them from the sidelines since they've first met. He feels indebted to them for getting him out from the strange 'other world' where he met and bonded with his persona, Marbas, ultimately deciding that, if it'll keep him safe, he's willing to work with Aislind to figure out what he's become.
That said, as they spend more and more time together, Sully finds themself wishing to understand Aislind more and more, and begin to spend time with them solely to interact with them. And as he does, perhaps he finds other feelings with them blooming, and perhaps he'll decide to approach them on those matters...
Aislind is at first suspicious of Sully, thinking him a demon (and, well, he kind of is, at the point they meet him). Then, they aren't sure what to think, after finding out he's just in a sort of... mutually-beneficial parasitic relationship with one. After all, they were created to eliminate demons, under the impression that demons were dangers to humans...
...and eventually, they are convinced to stick around him--if nothing else, he's still a person, and its still their job to protect those like him, right? And maybe they end up sticking around for longer than they expected, and maybe they end up developing an attachment of sorts...