Biomancer's Familiar

a Mutant attacks — 280 cards in the game can cause this (Biomancer's Familiar is one).

1. Wolverine, Claws Out — When Biomancer's Familiar attacks, Wolverine, Claws Out makes your creatures bigger

a Mutant deals combat damage — 280 cards in the game can cause this (Biomancer's Familiar is one).

1. Heroes in a Half Shell — When Biomancer's Familiar deals combat damage, Heroes in a Half Shell puts a counter on a permanent

a Mutant enters the battlefield — 286 cards in the game can cause this (Biomancer's Familiar is one).

When Biomancer's Familiar enters:

1. Genghis Frog — makes a token
2. X-23, Deadly Weapon — puts a counter on a permanent
3. April O'Neil, Live on the Scene — triggers

anything attacks — 17,934 cards in the game can cause this (Biomancer's Familiar is one).

When Biomancer's Familiar 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

489 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 (Biomancer's Familiar is one).

When Biomancer's Familiar 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

843 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 (Biomancer's Familiar is one).

When Biomancer's Familiar 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

131 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 (Biomancer's Familiar is one).

When Biomancer's Familiar attacks:

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

a creature it makes cheaper to cast — 19,392 cards in the game can cause this (Biomancer's Familiar is one).

Biomancer's Familiar reduces what:

1. Nakia, Wakandan Operative — costs
2. Liliana the Repentant — costs
3. Pious Evangel // Wayward Disciple — costs
4. Swarmborn Giant — costs
5. Goblin Goliath — costs
6. Sanctifier of Souls — costs
7. Ardoz, Cobbler of War — costs
8. Wispdrinker Vampire — costs
9. Black Panther, Wakandan King — costs
10. Distinguished Conjurer — costs

19,381 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 (Biomancer's Familiar is one).

When Biomancer's Familiar 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

3,030 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 (Biomancer's Familiar is one).

1. Prowl, Stoic Strategist // Prowl, Pursuit Vehicle — When Biomancer's Familiar enters, Prowl, Stoic Strategist // Prowl, Pursuit Vehicle puts a +1/+1 counter on itself

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