If something is cloaked magically from sight, why not use a completely different sense, right? But seeing how neither Childermass or Strange are adept at sniffing things and tracking that way, here's the other option: a weird dog. A really weird dog, since it looks like it's patterned more after a tiger than anything else. Still mostly dog-shaped, though.

"A Growlithe," Childermass says after a moment of silence, wondering if he might just be able to follow Strange in silence without having to answer that. It's a funny word. Most of these things are called ridiculous names, in fact, so he supposes Growlithe isn't the worst of them. Now, he doesn't sound embarrassed, per se, just... yeah. He has one, he has one of these bizarre little creatures. "The closest thing this world has to a working breed if what I've read is correct."

Of dog, of course. So, shepherds, mastiffs, and... Growlithe.