Mage of Doom: The path, at a price.
Mage seems to be the more active counterpart to Seer; if Seers illuminate the path for others, then Mages walk the path themselves. More than that, a Mage is a trailblazer: a Mage forges a path, guiding through actions where a Seer might guide with instructions and plans.
(Potentially of note: during much of her session, Rose was approximating a Mage of Void.)
And Doom? The word “doom” doesn’t mean death. It means condemned to an unpleasant and unavoidable fate. Doom comes from Anglo-Saxon dom: judgement, law. You probably already knew this meaning of doom, without quite being aware of it - it’s why in Christianity, “Doomsday” and “Judgement Day” are two names for the same thing. In Homestuck, “doomed” has another special meaning - it is what characterizes every timeline save the alpha. When Doc Scratch describes a doomed timeline, there is a strange implication that some kind of judgement is involved - that doomed timelines are judged and found wanting, and accordingly condemned.
So Doom can be laws, boundaries, rules: knowledge of the full dimensions of a system, and of the best way to work within it. (This is why Sollux is an excellent hacker; he understands the system and its rules and constraints, and he is magnificent at working within them.)
It can be judgments, in any sense of the word.
Sollux says it’s his own fault he was blinded and maimed? But it’s not surprising a Mage of Doom would judge himself harshly: what happened was well within the rules of Sgrub.
But the facet of Doom most useful for understanding Sollux’s arc is one particular rule:
Everything has a price.