Herald's Horn

an artifact is cast — 3,683 cards in the game can cause this (Herald's Horn is one).

When Herald's Horn 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 (Herald's Horn is one).

When Herald's Horn 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 (Herald's Horn is one).

When Herald's Horn 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

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

a creature it makes cheaper to cast — 19,392 cards in the game can cause this (Herald's Horn is one).

Herald's Horn reduces what:

1. Pollywog Prodigy — costs
2. Havengul Lich — costs
3. Saheeli, Radiant Creator — costs
4. Captain Jean-Luc Picard — costs
5. Windrider Wizard — costs
6. Master of Winds — costs
7. Invisible Woman — costs
8. Rockslide Sorcerer — costs
9. Umara Wizard // Umara Skyfalls — costs
10. Alania, Divergent Storm — costs

19,382 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 (Herald's Horn is one).

When Herald's Horn enters:

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

627 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 (Herald's Horn is one).

1. Sokka, Bold Boomeranger — When Herald's Horn is cast, Sokka, Bold Boomeranger puts a +1/+1 counter on itself

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