Doorkeeper

a card is milled — 772 cards in the game can cause this (Doorkeeper is one).

1. Lo and Li, Royal Advisors — When Doorkeeper makes a player mill a card, Lo and Li, Royal Advisors puts a counter on an Advisor

a card in a graveyard — 7,589 cards in the game can cause this (Doorkeeper is one).

1. Samwise Gamgee — Doorkeeper puts cards into the graveyard that Samwise Gamgee can bring back
2. Fire Nation Salvagers — Doorkeeper puts cards into the graveyard that Fire Nation Salvagers can bring back
3. Bloodbond March — Doorkeeper puts cards into the graveyard that Bloodbond March can bring back
4. Thor, God of Thunder — Doorkeeper puts cards into the graveyard that Thor, God of Thunder can bring back
5. Gale, Waterdeep Prodigy — Doorkeeper puts cards into the graveyard that Gale, Waterdeep Prodigy can bring back
6. Harness the Storm — Doorkeeper puts cards into the graveyard that Harness the Storm can bring back
7. Transplant Theorist — Doorkeeper puts cards into the graveyard that Transplant Theorist can bring back
8. Heart-Shaped Herb — Doorkeeper puts cards into the graveyard that Heart-Shaped Herb can bring back
9. Wayward Angel — Doorkeeper fills your graveyard toward the 7 or more cards Wayward Angel needs
10. Rescue from the Underworld — Doorkeeper puts cards into the graveyard that Rescue from the Underworld can bring back

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

anything goes to a graveyard — 7,589 cards in the game can cause this (Doorkeeper is one).

When a card hits the graveyard thanks to Doorkeeper:

1. The Haunt of Hightower — puts a +1/+1 counter on itself
2. Duskmantle Guildmage — makes each opponent lose 1 life
3. Vulturous Zombie — puts a +1/+1 counter on itself
4. Quest for Ancient Secrets — puts a quest counter on itself
5. Bloodchief Ascension — makes each opponent lose 2 life
6. Compost — draws you 1 card
7. Planar Void — hits a graveyard
8. Measure of Wickedness — gives an opponent control of itself
9. Energy Field — sacrifices itself

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

anything attacks — 17,934 cards in the game can cause this (Doorkeeper is one).

When Doorkeeper attacks:

1. Far Fortune, End Boss — deals 1 damage
2. Temmet, Naktamun's Will — draws you 1 card
3. Grim Javelineer — gives +1/+0
4. Invisible Woman — triggers
5. Caesar, Legion's Emperor — sacrifices a creature
6. Guide of Souls — triggers
7. Campsite Cuisine — sacrifices a Food
8. Gossip's Talent — triggers
9. Banon, the Returners' Leader — draws and discards
10. Toph, Earthbending Master — puts a counter on a permanent

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

a creature attacks — 17,934 cards in the game can cause this (Doorkeeper is one).

When Doorkeeper attacks:

1. Adaptive Omnitool — searches a library
2. Anthem of Rakdos — gives +2/+0
3. Kindred Discovery — draws you 1 card
4. Invasion of New Capenna // Holy Frazzle-Cannon — puts counters on a permanent
5. Chorale of the Void — brings a card back
6. Anim Pakal, Thousandth Moon — puts a +1/+1 counter on itself
7. Saw — sacrifices a creature
8. Gisa's Favorite Shovel — makes an opponent sacrifice a creature
9. Ultima Weapon — kills a creature an opponent controls
10. Total War — kills a creature

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

a creature blocks — 17,934 cards in the game can cause this (Doorkeeper is one).

When Doorkeeper blocks:

1. Mage Hunters' Onslaught — makes a player lose 1 life
2. Carnage Gladiator — makes a player lose 1 life
3. Perimeter Captain — gains you 2 life
4. Tide of War — sacrifices a creature
5. Dead-Iron Sledge — kills a creature
6. Dwindle — kills a creature

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

a creature deals combat damage — 17,934 cards in the game can cause this (Doorkeeper is one).

1. Primo, the Unbounded — When Doorkeeper deals combat damage, Primo, the Unbounded makes a token

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

a nontoken creature attacks — 17,934 cards in the game can cause this (Doorkeeper is one).

1. Mardu Ascendancy — When Doorkeeper attacks, Mardu Ascendancy makes a token

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

a creature enters the battlefield — 19,800 cards in the game can cause this (Doorkeeper is one).

When Doorkeeper enters:

1. Slash, Reptile Rampager — deals 2 damage
2. Ray Fillet, Wave Warrior — puts a counter on itself
3. The Neutrinos — gets +1/+0
4. Wingnut, Bat on the Belfry — grants flying, haste and menace
5. Aetherstorm Roc — puts a counter on a permanent you control
6. Raphael, Most Attitude — exiles a card from your library

341 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 (Doorkeeper is one).

1. Prowl, Stoic Strategist // Prowl, Pursuit Vehicle — When Doorkeeper enters, Prowl, Stoic Strategist // Prowl, Pursuit Vehicle puts a +1/+1 counter on itself

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