Resonance

[Silarn]

So in some of the recent WoB, such as this recent q&a, a newish concept of Resonance has come up. That may or may not be a final, cannon name for the concept.

From what we've learned so far, a Resonance is a sort of side-effect, alteration, or improvement on a core investiture gained by the combining of two different magics. The two merge in some way, causing a change or extension in how the magics work.

It's also suggested that Waxilium's ability to carefully bend projectiles around himself, such as the bubble, or carefully guiding projectiles to a new path. His potential savant status with both steel and iron greatly improves this ability - but without the interaction of both powers, this ability to bend and direct the projectiles may not exist.

I think it's also possible this can explain Lift's unique traits: her ability to touch Spren and create Stormlight by digesting food. It's been heavily implied that these are only tangential affects of her Boon/Curse by the Old Magic - they are side effects with how the Boon/Curse of the Old Magic interacted with the powers of a Surgebinder.

I'm not sure if this is fleshed out or non-theory enough to put up on Coppermind, but I thought I'd suggest it.

Edited April 5, 2017 by Silarn
Revising a little - I perhaps took the wrong part of Lift's lore

[Silarn]

Brandon also specifically mentions that while Truthwatchers and Lightweavers are technically able to Lightweave - due to the binding of Illumination - this power manifests a bit differently for each combination.