Do you think Pallas is a Darkin?

It's something we're all waiting to be confirmed or nah'd by Riot. The foundations team are up to something with him though.

EDIT: Actually I've done some snooping. Jaredan recently answered another question on Varus on his ask.fm relating to his arclight canonicity.

I keep hearing that some un-named rioter supposedly said Arclight Varus is canonically what Varus was pre-corruption. I can't imagine that's literally the case. I'll buy that was his skin- & hair-color, sure, but not the clothes and light-powers surely? Can you confirm what the case actually is?

Yup, he wasn't all glowy before the thing that happened to make Varus so Varusy. And there are a number of other things that make Arclight non-canonical to Varus that we'll reveal some point soon. I could tell you which point, but then I'd find a corrupted arrow in my sternum.

Most likely. Although it would be pretty funny if varus wasnt and rhaast just kept mistaking him for one of his darking brethren due to how long its been sonce they were together.