Floating Shield
Most protection auras commit to a single creature and stand or fall with it; this one builds an exit door into the same card. While it sits granting protection from a chosen color, the real flexibility lives in the sacrifice clause: at instant speed, you can cash the aura in to hand that same protection to any creature for a turn. That mode answers the chronic problem with a color-locked protection aura, which is that it becomes dead weight once the named color stops mattering or the host starts looking doomed. Rather than rot on a creature you no longer want it on, the aura can leave the battlefield doing work: blanking a chosen-color removal spell aimed elsewhere, or pushing a different attacker past a chosen-color blocker. You spend one card and walk away having spent it on a real effect. The rigidity it never sheds is the color choice itself, locked as it enters and never updated, so committing to the wrong color early is the cost of the option. Note that this is no insurance against a kill spell cast in response to the aura: a removed host orphans the aura on the stack, and it never enters to be sacrificed. The clause stating the effect does not remove the aura is a genuine rules patch, not flavor: protection from white would otherwise cause a white aura to fall off the creature it just landed on, and this line keeps it attached.
