Head and Hands

Question: What knack would instantly learning sign language fall under?

Ooh, neat question! We suggest a couple of possibilities.

First of all, Language Mastery could easily be said to learn sign language (ASL, BSL, IS or any other variation) as well as any spoken tongue. Sign language is still a language, after all, just one communicated with signs instead of noises, so there's no reason to exclude it from the knack if you don't want to. If you want to separate sign language from normal speech, you could also say that it can be learned by anyone with the Instant Translation, working on the theory that sign language and written language are both visual means of communication.

In the past, we've also allowed the Cipher knack to be used with sign language; since signs represent words and are basically similar to codes, we've allowed Scions to play charades with Cipher that are so effective they basically become a language in and of themselves. This method has the additional fun of allowing the Scions using it not to be "overheard" by anyone who doesn't also have Cipher, since the code would be incomprehensible to anyone not suited to cracking it.

A Scion's who's rolling with Perfect Impostor might also be able to fake it in a sign language conversation under certain circumstances; while we wouldn't say that she could actually learn the language that way, she might be able to figure out on the fly how to make or read certain basic gestures to use in the moment that she could remember later (especially if she also has Perfect Memory).

Raw Epic Intelligence can also be used to learn languages, though not instantly without any work. A Scion with decent Epic intelligence and Academics who spends some time learning sign language in-game should also be able to pick it up fairly easily, though it would take some time to do so.