Totally fitting.
It fits to a T. The intro makes me visualize Singed concocting a new poisonous brew, and the increasing intensity gives one the image of smoke and vapor rising from beakers and test tubes, slowly filling the room. A perfect song for Singed. The only constructive criticism I have to offer would be the "How about a drink." I guess it might make one think of Singed offering a poisoned flask to someone, but when I heard that vocal I immediately thought of Gragas offering some lucky chap one of his fine brews. So constructive criticism: Maybe change the vocal track? If not for that, I'd have given 10/10. Great job.