Mage: Someone who guides others with knowledge of their aspect. They have a talent for hearing their exiles exceptionally well like Seers do. Rather than gaining knowledge using their aspect, mages will gain knowledge directly from it, and understand the rules of it. The differing methods of gaining knowledge may blur into each other a little depending on the aspect. But mages will always have an emphasis on understanding how their aspect actually works and avoiding or gaining it, or in a few cases, it's inevitability. They lack their aspect within themselves in exchange for protection from their aspect.

Blood: Bonds, trust, unity, and connections with others. Leadership and inspiration. They would be protagonists in an rpg, and friendship is their strength.

I'll get the part that I was initially the most unsure about out of the way first. Mages lack their aspect or avoid it in exchange for protection from it, given that Meulin was a Mage of Heart and avoids any real lasting heartbreak or even severe trauma from the incident that made her deaf, and Sollux is a Mage of Doom but somehow kept on avoiding complete death. I don't think that a Mage of Blood would lack bonds as a whole, given that would make their entire classpect kind've impossible to fulfill. However, I think the right way of looking at it is that while they can guide others, they are nowhere near fit for or have no interest in an actual leadership position. The protection they gain from that is simply that they can tell whenever the person in the leadership position is corrupt or untrustworthy, and guide others with that knowledge as well.

They would act more like the advisor to a leader than anything else. Their advice would be exceptionally useful but for things like combat, they wouldn't be able to make plans or help boost their teams morale. But, they would lead the team leader towards knowing how to inspire everyone, because the Mage would help them strengthen their bonds. They would also know when there's someone untrustworthy that they should not make a pact with, or at least treat with a lot of caution, similar to how Terezi was able to tell that Jack Noir wasn't someone Karkat should trust completely, even though they still used their pact with him and his gang to their advantage.

They would have a deep understanding of their friendships and bonds with their teammates and anyone else that they know. They would probably help others make friends, like if there was a player in their session that wasn't particularly close to any of the others, the Mage of Blood would guide them towards friendship.

I feel like this could be more fleshed out in a way I can't figure out at the moment, and might make an addendum for it. But I also feel like this is a really simple to explain class, blood players tend to lack combat abilities that are actually related to their classpect, except in cases where they're fit for leadership positions and utilize their bonds for fighting, and a mage is exempt from that ability. So it probably just feels shorter cause of that?

Later today I go dog-sitting and I'm unsure if I'll be able to post much more until Sunday so I'm trying to do these a bit earlier than usual.