Petrahydrox

a nontoken creature leaves the battlefield — 4,133 cards in the game can cause this (Petrahydrox is one).

When Petrahydrox leaves the battlefield:

1. Tokka & Rahzar, Unsupervised — puts a +1/+1 counter on itself
2. Splinter, the Mentor — makes a token
3. Rat King, Pale Piper — makes a token
4. Dual Nature — exiles a creature

a creature leaves the battlefield — 4,238 cards in the game can cause this (Petrahydrox is one).

When Petrahydrox leaves the battlefield:

1. Lunarch Veteran // Luminous Phantom — gains you 1 life
2. Extractor Demon — mills a card
3. Aang, Airbending Master — puts a counter on a permanent
4. Dour Port-Mage — draws you 1 card
5. Vela the Night-Clad — makes each opponent lose 1 life
6. Taeko, the Patient Avalanche — scries
7. Ninth Bridge Patrol — puts a +1/+1 counter on itself
8. Funeral March — makes a player sacrifice a creature
9. Sally Sparrow — triggers
10. Aang, at the Crossroads // Aang, Destined Savior — triggers

21 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 (Petrahydrox is one).

When Petrahydrox attacks:

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

112 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 (Petrahydrox is one).

When Petrahydrox 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

180 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 (Petrahydrox is one).

When Petrahydrox blocks:

1. Mage Hunters' Onslaught — makes a player lose 1 life
2. Carnage Gladiator — makes a player lose 1 life
3. Barrow-Blade — strips abilities
4. Heat of Battle — deals 1 damage
5. Battle Strain — deals 1 damage
6. Favor of the Woods — gains you 3 life
7. Tide of War — sacrifices a creature
8. Dead-Iron Sledge — kills a creature
9. Dwindle — kills a creature
10. Shield of the Righteous — triggers

18 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 (Petrahydrox is one).

When Petrahydrox attacks:

1. Mardu Ascendancy — makes a token
2. Basri Ket — makes a token
3. Militia's Pride — makes a token

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

When Petrahydrox deals combat damage:

1. Locutus of Borg — makes a token
2. Antagonist Incorporator — makes a token
3. Hive Mind Coprocessor — makes you lose life

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

a creature is cast — 18,010 cards in the game can cause this (Petrahydrox is one).

When Petrahydrox is cast:

1. Champions of the Perfect — draws you 1 card
2. Primeval Bounty — makes a token
3. Bloodbond March — brings a card back

88 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 (Petrahydrox is one).

When Petrahydrox 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

299 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 (Petrahydrox is one).

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

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