River Heralds' Boon

a creature gets a counter — 2,691 cards in the game can cause this (River Heralds' Boon is one).

When a Merfolk gets a counter thanks to River Heralds' Boon:

1. Hollowmurk Siege — draws you 1 card
2. Ant-Man, Colony Commander — makes a token
3. Earth Kingdom General — gains you that much life
4. Casey Jones, Back Alley Brute — deals that much damage
5. Generous Patron — draws you 1 card
6. Shalai and Hallar — deals that much damage
7. Danny Pink — draws you 1 card
8. Enduring Scalelord — puts a +1/+1 counter on itself
9. Bold Plagiarist — puts counters on a permanent
10. Mikey & Leo, Chaos & Order — draws you 1 card

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

an instant is cast — 3,931 cards in the game can cause this (River Heralds' Boon is one).

When River Heralds' Boon is cast:

1. Lunar Mystic — draws you 1 card
2. Ojer Pakpatiq, Deepest Epoch // Temple of Cyclical Time — grants rebound
3. Repeated Reverberation — copies an ability
4. Bill Potts — copies an ability
5. Riku of Two Reflections — copies a spell
6. Sword of Wealth and Power — copies a spell
7. Lilah, Undefeated Slickshot — gets +1/+1
8. Gale, Waterdeep Prodigy — brings a card back
9. In the Eye of Chaos — counters a spell
10. Niblis of Frost — taps a creature an opponent controls

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

anything gets a counter — 4,415 cards in the game can cause this (River Heralds' Boon is one).

1. All Will Be One — When a Merfolk gets a counter thanks to River Heralds' Boon, All Will Be One deals that much damage

7 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 (River Heralds' Boon is one).

When River Heralds' Boon is cast:

1. Windrider Wizard — draws you 1 card
2. Relic Amulet — puts a charge counter on itself
3. Rockslide Sorcerer — deals 1 damage
4. Umara Wizard // Umara Skyfalls — grants flying
5. Alania, Divergent Storm — makes an opponent draw 1 card
6. Umara Mystic — gets +2/+0
7. Master of Winds — triggers

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