Anthriss is the last of the Challenge Tames that I’ve yet to tame, so I unfortunately cannot speak from experience. And I doubt I ever will, for two reasons.
The first is that Anthriss spawns in a very easy location to get to. As a result, any hunter happening to work on dailies, rather than Rare Hunters, will be able to see him, and probably kill him rather than tame him, as he is a little bit difficult.
The second reason is that he is not a unique skin. Anthriss shares his skin with Cinderweb Creepers, which spawn in the Forlorne Spire. As real-estate in my stable is at a premium right now, I won’t be sacrificing one of my truly unique pets in order to tame a spider that shares a skin, as I’ve already got 4 other spiders. I may have to drop Kirix and Skitterflame soon from my stable…
Anthriss’ sole ability you need to worry about is Searing Webs. This ability casts flaming webs on you, dealing Fire Damage over time. The fire damage (from what I’ve read) makes taming impossible.
However, there is a way to get around it. Simply stand in one of the lava pools near his spawn location. Skitterflame has a 12 hour spawn timer. I’ve actually only seen him once and that was a corpse. As I wrote earlier, the real challenge with Anthriss, as with Arcturis, is that he is the easiest challenge spawn to find.
Once inside the pool (you must be completely submerged so that a breath bar appears) simply tame and enjoy your new pet. I’m sorry I can’t give any greater detail on this tame, but hopefully the video below will be more informative.