Arena

a creature becomes tapped — 565 cards in the game can cause this (Arena is one).

1. Seedship Agrarian — When Seedship Agrarian becomes tapped thanks to Arena, it makes a token
2. Unctus, Grand Metatect — When a creature becomes tapped thanks to Arena, Unctus, Grand Metatect draws you 1 card
3. Sharae of Numbing Depths — When a creature becomes tapped thanks to Arena, Sharae of Numbing Depths draws you 1 card
4. Rewrite History — When a creature becomes tapped thanks to Arena, Rewrite History draws you 1 card
5. Stinging Licid — When a creature becomes tapped thanks to Arena, Stinging Licid deals 2 damage
6. Gideon's Avenger — When a creature becomes tapped thanks to Arena, Gideon's Avenger puts a +1/+1 counter on itself
7. Icewrought Sentry — When a creature becomes tapped thanks to Arena, Icewrought Sentry gets +2/+1
8. Cryoshatter — When a creature becomes tapped thanks to Arena, Cryoshatter kills a creature
9. Don't Move — When a creature becomes tapped thanks to Arena, Don't Move kills a creature
10. Hylda of the Icy Crown — When a creature becomes tapped thanks to Arena, Hylda of the Icy Crown triggers

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

a creature deals noncombat damage — 1,420 cards in the game can cause this (Arena is one).

When a creature deals noncombat damage thanks to Arena:

1. Soul Link — gains you that much life
2. Tandem Lookout — draws you 1 card
3. Armadillo Cloak — gains you that much life
4. Vampiric Link — gains you that much life
5. Spirit Loop — gains you that much life
6. Spirit Link — gains you that much life
7. Guilty Conscience — deals that much damage
8. Visions of Brutality — makes a player lose life equal to that much
9. Arm with Aether — triggers

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

a land enters the battlefield — 1,560 cards in the game can cause this (Arena is one).

1. Primeval Bounty — When Arena enters, Primeval Bounty gains you 3 life
2. Toph, Earthbending Master — When Arena enters, Toph, Earthbending Master puts a counter on a permanent
3. Dancing from Dark to Dawn — When Arena enters, Dancing from Dark to Dawn makes a token
4. Emeria Shepherd — When Arena enters, Emeria Shepherd brings a card back
5. Quest for the Necropolis — When Arena enters, Quest for the Necropolis puts a quest counter on itself
6. Soul Stair Expedition — When Arena enters, Soul Stair Expedition puts a quest counter on itself
7. Nissa of Shadowed Boughs — When Arena enters, Nissa of Shadowed Boughs puts counters on a permanent
8. Thranduil, Sindarin Liege // Silvan Rally — When Arena enters, Thranduil, Sindarin Liege // Silvan Rally makes a token
9. Silvan Reveler — When Arena enters, Silvan Reveler returns itself from the graveyard
10. Floral Evoker — When Arena enters, Floral Evoker puts a +1/+1 counter on itself

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

anything deals noncombat damage — 3,068 cards in the game can cause this (Arena is one).

When a creature deals noncombat damage thanks to Arena:

1. Quest for Pure Flame — puts a quest counter on itself
2. Soul-Scar Mage — puts that many counters on a permanent
3. Fear of Burning Alive — deals that amount damage
4. Niv-Mizzet, Visionary — draws you that many cards
5. Chandra's Incinerator — deals that much damage
6. Chandra's Pyreling — gets +1/+0
7. Talon of Pain — puts a charge counter on itself
8. Asgardian Inspiration — returns itself from the graveyard
9. Thor, Guardian of Midgard — exiles a card from your library
10. Virtue of Courage // Embereth Blaze — exiles a card from your library

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

a creature is dealt damage — 18,923 cards in the game can cause this (Arena is one).

When a creature is dealt damage thanks to Arena:

1. Kazarov, Sengir Pureblood — puts a +1/+1 counter on itself
2. Jennifer Walters // The Sensational She-Hulk — deals that much damage
3. Shriveling Rot — kills it
4. Hot Soup — kills a creature
5. Cracked Skull — kills a creature
6. Sporogenic Infection — kills a creature
7. Frozen Solid — kills a creature
8. Mortal Wound — kills a creature
9. Mire Blight — kills it
10. Death Pits of Rath — kills it

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