Mourner's Shield

Most imprint artifacts read off a card's mana value, its name, or some splashy attribute and turn that into a mechanical payload. This one reads off the exiled card's color, then uses that color as a filter for damage prevention, which is a genuinely odd circuit. You exile a card from any graveyard, note its color or colors, and from then on the activated ability can fog one source per turn so long as that source shares a color with the imprinted card. The catch is built into the dependency: whatever color you find in a graveyard is the only color this shield ever cares about. Imprint something white and you can blank a white attacker or burn spell, but only white ones, and only the single source you pick per turn. It is a prevention shield that arrives pre-tuned to the threats already lying dead, defined entirely by a card someone has discarded, milled, or killed. That conditionality makes it slow and narrow, but it also means the imprint clause does double duty as light graveyard hate, exiling a target before anyone can recur it. The whole apparatus is colorless by type and color by function, a small monument to the idea that the cleanest way to give an artifact a color identity is to borrow one from the dead.