one piece the four emperors booster box op 09 Amazon.com: Japanese OP-09 Booster Box One Piece TCG : Toys & Games Each Booster Box Contains 24 Booster Packs A Special Booster Pack to Commemorate the 2nd Anniversary One Piece OP09 The Four

They rarely appear for sale and when they do they never seem to sell

But they both "replace" themselves in terms of mana, making for easy ramp, and can be traded for another card at any point in the game (ideally once the field is full of other artifacts)

A card that has been trimmed with scissors or a paper cutter to remove the rounded corners can superficially resemble a genuine square-cut error

Bean Soldier

Meanwhile Battle for Baldurs Gate brought us mono-color Gates

Final Fantasy is introducing an entire cycle of artifact cards that look quite powerful in Commander, some of which have some powerful replacement effects for focused strategies