If you control Mox Opal and one other artifact, then have a second Mox Opal enter the battlefield as your third artifact, you can't activate either one's mana ability before putting one into your graveyard due to the “legend rule.”
Mox Opal
This printing is one of 3 catalogued treatments from PRM — the lineup includes Foil and Nonfoil alongside the standard finish. Across our catalog the Rarix library tracks every variant in the same family so collectors can compare price, scarcity and demand inside a single lineage.
This card belongs to *Magic Online Promos* (released August 2020).
Card #82856 in Magic Online Promos.
Rarity tier: mythic. Mythic rares historically land in roughly one out of every eight boosters at standard print densities.
Card type: Legendary Artifact. Mana cost: {0} (0 converted). Keyword abilities: Metalcraft.
Legal in Modern, Legacy, Vintage, Commander, and Brawl. Banned in Historic.
EDHrec ranks this card #238 in Commander, putting it in the popular-include tier of the format's playable pool.
Illustrated by Martina Pilcerova. Rarix tracks 404 other cards credited to this artist across the catalog — browse the full gallery to see the body of work.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Martina Pilcerova
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
