Irradiate

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

When you cast Irradiate, it counts:

1. Chimeric Egg — and does more
2. Prowl, Stoic Strategist // Prowl, Pursuit Vehicle — and does more
3. HYDRA Assault Robot — and does more
4. Tome of Legends — and does more
5. Canoptek Spyder — and does more
6. Cloudstone Curio — and does more
7. Traxos, Scourge Eternal — and does more
8. Alibou, Ancient Witness — and does more
9. Foot Chopper — and does more
10. Lux Artillery — and does more

3,631 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 (Irradiate is one).

When Irradiate 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. Riku of Two Reflections — copies a spell
5. Sword of Wealth and Power — copies a spell
6. Lilah, Undefeated Slickshot — gets +1/+1
7. Gale, Waterdeep Prodigy — brings a card back
8. Harness the Storm — 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 is cast — 31,128 cards in the game can cause this (Irradiate is one).

When Irradiate 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.