Undertaker

a creature leaves a graveyard — 1,302 cards in the game can cause this (Undertaker is one).

When Undertaker leaves a graveyard:

1. Grim Reaper's Scythe — makes a token
2. Syr Konrad, the Grim — deals 1 damage
3. Cyan, Vengeful Samurai — puts a +1/+1 counter on itself
4. Along the Crooked Way — puts a counter on a Goblin or Army
5. Skeleton Crew — makes a token
6. Desecrated Tomb — makes a token
7. Chalk Outline — makes a token
8. Insidious Roots — makes a token
9. Undead Hand Ninja — makes each opponent lose 1 life
10. Rot Farm Mortipede — gets +1/+0

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

a card is discarded — 2,042 cards in the game can cause this (Undertaker is one).

When Undertaker makes a player discard a card:

1. Ivora, Insatiable Heir — puts a +1/+1 counter on itself
2. Cool but Rude — deals 2 damage
3. Containment Construct — brings a card back
4. Moonstone, Harsh Mistress — brings a card back
5. Lazotep Chancellor — puts 2 counters on a Zombie or Army
6. Magmakin Artillerist — deals that much damage
7. Inti, Seneschal of the Sun — exiles a card from your library
8. Pitchstone Wall — sacrifices itself
9. Currency Converter — exiles it
10. Hostile Investigator — triggers

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

anything leaves a graveyard — 2,503 cards in the game can cause this (Undertaker is one).

When Undertaker leaves a graveyard:

1. Blastoneuron — makes each opponent lose 1 life
2. Defiled Crypt // Cadaver Lab — makes a token
3. Teval, the Balanced Scale — makes a token
4. Hologram Stalker — makes a token
5. Tormod, the Desecrator — makes a token
6. Quintorius, Field Historian — makes a token
7. Garrison Excavator — makes a token
8. Amzu, Swarm's Hunger — makes a token
9. Kirol, History Buff // Pack a Punch — becomes prepared
10. Teval's Judgment — triggers

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

a Human enters the battlefield — 4,639 cards in the game can cause this (Undertaker is one).

When Undertaker enters:

1. General Kudro of Drannith — hits a graveyard
2. Heronblade Elite — puts a +1/+1 counter on itself
3. Kyler, Sigardian Emissary — puts a +1/+1 counter on itself
4. Thalia's Lieutenant — puts a +1/+1 counter on itself
5. Champion of the Parish — puts a +1/+1 counter on itself
6. Captain of the Mists — untaps itself
7. Erkenbrand, Lord of Westfold — gives +1/+0
8. Beregond of the Guard — gives +1/+1
9. Théoden, King of Rohan — grants double strike
10. Lossarnach Captain — taps a creature an opponent controls

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

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

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

When a card hits the graveyard thanks to Undertaker:

1. Quest for Ancient Secrets — puts a quest counter on itself
2. Planar Void — hits a graveyard
3. Measure of Wickedness — gives an opponent control of itself
4. Energy Field — sacrifices itself

7 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 (Undertaker is one).

When Undertaker attacks:

1. Far Fortune, End Boss — deals 1 damage
2. Temmet, Naktamun's Will — draws you 1 card
3. Invisible Woman — triggers
4. Caesar, Legion's Emperor — sacrifices a creature

124 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 (Undertaker is one).

1. Adaptive Omnitool — When Undertaker attacks, Adaptive Omnitool searches a library

199 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 (Undertaker is one).

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

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