[renowner]

Yeah But Mass Summon eats up about 150 fp a turn. (And summons them randomly, sometimes in places they can't even fight!)
Shine knights have a Blindness aura, and about 700+ Health each, and no upkeep, and last forever. As a D rank invoke it'd be too strong.
Maybe as a D rank invoke, it only summons one knight? I think that'd be fine. 9m for one knight seems perfectly fine to me. You only really need the one knight for the blindness aura, so it'd probably be stronger even.