The ultimate ability, so terrifying that it shall not be used under any circumstance.
SpecsGastro describes his occupation as that of a “Scholar.” One who finds the Truth and exposes it to others. Yet, he believes that the Truth is subjective, for everyone to decide for themselves what is True or not.
It is this discrepancy between Objective and Subjective Truth that allows for this ability to exist.
Using his supreme magic, Specs may take his Truth, the subjective one, and supplant a target’s own subjective Truth. Such a forcible change causes the universe itself to shift to correct the difference, effectively creating a new “Objective” Truth.
Put more simply, if he decides something is True, Specs can make it so that it is. And with such an indomitable will as he possesses, even circumstances that are clearly not possible will become True with this ability.
Put even more simply, it is pure and straight reality manipulation with very little constraint or shortcomings.
And yet, he refuses to use it.
“Who am I but a humble slug to decide for others what the Truth ought to be? To me, it may appear to be a better outcome. To me, it may appear to be for the good of the universe and save countless lives. But I am merely me, and no one else. It is not for me to decide, and so, it is not a power for me to use.”
Perhaps, in a highly emotional state, he could be persuaded.
Weaknesses? Well… It needs to have a target, but it could probably be used on himself in a pinch. Maybe there are Truths even Specs cannot believe?