The floating cube can simply declare that reality is constant and absolute and enforce it to negate reality-warping >:]] (unless you can interrupt it before it can finish its sentence; and even if it does successfully execute the ability lock, your character might still have ways to threaten the cube/deal with its attacks).
Since they in the same group though, I don't think a conflict would possibly erupt between them. Heck, he might even declare that reality is actually unstable and dependent on the mind then enforce it as a colossal buff for your character should they ever team up in combat. The Author's fighting style specializes in manipulation and calculated moves, so our characters are prolly foils of each other in a sense.