Heir: Someone who inherits their aspect by being given it, and/or representing/becoming their aspect, physically or metaphorically. They start out with their aspect affecting and controlling them on its own will, being saved or helped by their aspect when they’re in trouble, and eventually learn to consciously use it as they “inherit” it.

Light: Knowledge, particularly narrative knowledge and narrative importance (spotlight), fortune, luck, literal light, foresight, literal sight. Often associated with emotional instability, likely due to the trope of people going mad when they've attained too much knowledge.

So, I guess an Heir of Light would oppose a Seer of Light because of the way they go about attaining knowledge in the at first. Heirs are sort've at the mercy or grace of their aspect in the beginning. So, I suppose an Heir of Light would start out not really seeking any knowledge out at all, knowledge would simply find them instead. Skaia's clouds or the Horrorterrors above Derse would be a good way to go about this, but they could also simply stumble onto an object that gives them knowledge or just happen to find themselves in the right places at the right time. The luck part of light would stay mostly the same, but they would grow more and more lucky the more powerful they got. An Heir of Light that reaches their full potential would be on par with, if not luckier, than Clover.

Breath and Light have something in common, which is that they're incredibly meta aspects. Breath relates to narrative freedom, and Light relates to narrative importance. Either way, it would lead to a character that's incredibly relevant in the story if not just the main protagonist. Some of my analysis's are speculation and could have other plausible interpretations, but all my responses are rooted in information I've gleaned from the comic and try to be as canon compliant as possible. I can't say everything that I say is 100% true and non-debatable, but the fact that an Heir of Light would inherit the position as the most important character in their comic is something that is undeniably true. They inherit luck, they inherit a full and comprehensive understanding of the story and world around them, and they inherit the spotlight. They don't even need to steal it like Vriska does. It's just theirs.

So please, assign yourself Heir of Light as your own classpect responsibly lol.

I wonder how similar my interpretation is to the person who requested it, I'm interested in all the replies I get that aren't just requests even if I don't respond to them directly. I promise I read and appreciate each one ^^