Sanctuary Blade

Protection is the swingiest keyword in combat because it collapses several effects into one word: the equipped creature cannot be blocked by, dealt damage by, targeted by spells or abilities of, or enchanted and equipped by things of the chosen color. The clever part of this piece is that it hands you that toolkit at attach time rather than at deckbuilding time. The color is chosen fresh every time the blade moves, so the same hardware answers a red board one turn and a black removal spell the next. That flexibility is the whole appeal, and it is also the ceiling: protection only reaches the color you name, so against a table running everything, one attacker is still cold to every other color's blockers and burn. You are betting on reading the most dangerous threat correctly at the moment you equip. The +2/+0 is almost incidental, a reason to keep the creature swinging while the protection does the real work of pushing past a same-color blocker or dodging a same-color kill spell. It sits in the long line of protection-granting gear, but where older pieces locked you into one color permanently, this one lets you re-aim the shield each time it changes hands. The equip cost is what keeps that repositioning deliberate rather than free: the mobility that makes the blade interesting is also the tax you pay to use it turn after turn.