Pledge of Loyalty

Protection here reads your own battlefield rather than the opponent's, which is the inversion that makes it tick: the enchanted creature gains protection from exactly the colors of permanents you control, so the shield is parasitic on your board state and reshapes itself as your side of the table changes. The catch hides in plain sight. A mono-white deck turns this into protection from white, and protection from white would ordinarily mean the white Aura granting it slides off the instant it resolves. The clause "this effect doesn't remove this Aura" is what keeps the card from devouring itself: it lets the Aura survive granting protection from its own color, so the grant holds instead of self-destructing. The upside scales with the breadth of your board: the more colors you control, the more colors the creature can ignore in combat and in damage prevention, which widens both its evasion and its defensive cover. A creature protected from white, blue, black, red, and green is functionally unblockable and largely untargetable, and a sufficiently many-colored board gets it most of the way there. That makes this a reward for diversity of permanents rather than focus, an unusual ask for white, and a clever recasting of the usual "protection from a chosen color" template into something that interrogates the state of your own side rather than naming an enemy.