Mox Opal

an artifact you control — 3,641 cards in the game can cause this (Mox Opal is one).

1. Relic Amulet — Relic Amulet counts toward the 3 or more artifacts Mox Opal needs
2. Chimeric Egg — Chimeric Egg counts toward the 3 or more artifacts Mox Opal needs
3. Prowl, Stoic Strategist // Prowl, Pursuit Vehicle — Prowl, Stoic Strategist // Prowl, Pursuit Vehicle counts toward the 3 or more artifacts Mox Opal needs
4. Tome of Legends — Tome of Legends counts toward the 3 or more artifacts Mox Opal needs
5. Canoptek Spyder — Canoptek Spyder counts toward the 3 or more artifacts Mox Opal needs
6. Sword of Wealth and Power — Sword of Wealth and Power counts toward the 3 or more artifacts Mox Opal needs
7. Cloudstone Curio — Cloudstone Curio counts toward the 3 or more artifacts Mox Opal needs
8. Traxos, Scourge Eternal — Traxos, Scourge Eternal counts toward the 3 or more artifacts Mox Opal needs
9. Alibou, Ancient Witness — Alibou, Ancient Witness counts toward the 3 or more artifacts Mox Opal needs
10. Foot Chopper — Foot Chopper counts toward the 3 or more artifacts Mox Opal needs

3,630 other cards care about it too. These are the ones with the most connections.

an artifact is cast — 3,683 cards in the game can cause this (Mox Opal is one).

When Mox Opal is cast:

1. Mendicant Core, Guidelight — copies a spell
2. Sai, Master Thopterist — makes a token
3. Ravenous Robots — makes a token
4. Pinnacle Emissary — makes a token
5. Mirrodin Besieged — makes a token
6. Poetic Ingenuity — makes a token
7. Digsite Engineer — makes a token
8. Myrsmith — makes a token
9. Riddlesmith — draws you 1 card
10. Dr. Madison Li — puts a counter on a permanent you control

271 other cards care about it too. These are the ones with the most connections.

a nontoken artifact enters the battlefield — 3,768 cards in the game can cause this (Mox Opal is one).

When Mox Opal enters:

1. Ultron, Artificial Malevolence — makes a token
2. The Prydwen, Steel Flagship — makes a token
3. Conquest Mission — puts a quest counter on itself
4. Surge Conductor — proliferates
5. Replication Specialist — makes a token
6. Weapons Manufacturing — makes a token
7. Mirrorworks — makes a token

an artifact enters the battlefield — 4,643 cards in the game can cause this (Mox Opal is one).

When Mox Opal enters:

1. Transplant Theorist — draws you 1 card
2. Elvish Archivist — puts 2 +1/+1 counters on itself
3. Golbez, Crystal Collector — surveils
4. Sludge Strider — makes a player lose 1 life
5. Underhanded Designs — makes each opponent lose 1 life
6. Mechan Assembler — makes a token
7. Glassdust Hulk — gets +1/+1
8. Rook Turret — draws you 1 card
9. Hedron Detonator — deals 1 damage
10. Pactdoll Terror — makes each opponent lose 1 life

55 other cards care about it too. These are the ones with the most connections.

anything enters the battlefield — 26,499 cards in the game can cause this (Mox Opal is one).

When Mox Opal enters:

1. HYDRA Assault Robot — deals 1 damage
2. Era of Innovation — puts a counter on a permanent you control

38 other cards care about it too. These are the ones with the most connections.

anything is cast — 31,128 cards in the game can cause this (Mox Opal is one).

When Mox Opal is cast:

1. Sokka, Bold Boomeranger — puts a +1/+1 counter on itself
2. Saheeli, Radiant Creator — puts a counter on a permanent you control

10 other cards care about it too. These are the ones with the most connections.