Blood Researcher

a Vampire attacks — 484 cards in the game can cause this (Blood Researcher is one).

When Blood Researcher attacks:

1. Glass-Cast Heart — makes a token
2. Sanctum Seeker — makes each opponent lose 1 life

a nontoken Vampire attacks — 484 cards in the game can cause this (Blood Researcher is one).

1. Mavren Fein, Dusk Apostle — When Blood Researcher attacks, Mavren Fein, Dusk Apostle makes a token

a Vampire creature is cast — 484 cards in the game can cause this (Blood Researcher is one).

1. Bloodlord of Vaasgoth — When Blood Researcher is cast, Bloodlord of Vaasgoth grants bloodthirst

a Vampire deals combat damage — 484 cards in the game can cause this (Blood Researcher is one).

When Blood Researcher deals combat damage:

1. Rakish Heir — puts a counter on a permanent
2. Stensia Masquerade — puts a counter on a permanent

a Vampire enters the battlefield — 500 cards in the game can cause this (Blood Researcher is one).

When Blood Researcher enters:

1. Anje, Maid of Dishonor — makes a token
2. Forerunner of the Legion — gives +1/+1
3. Markov Enforcer — deals damage
4. Evelyn, the Covetous — exiles a card from a library

gain life — 2,076 cards in the game can cause this.

1. Primeval Bounty — When Primeval Bounty gains life, Blood Researcher puts a +1/+1 counter on itself
2. Massacre Girl, Most Wanted — When Massacre Girl, Most Wanted gains life, Blood Researcher puts a +1/+1 counter on itself
3. Ayara, First of Locthwain — When Ayara, First of Locthwain gains life, Blood Researcher puts a +1/+1 counter on itself
4. Gala Greeters — When Gala Greeters gains life, Blood Researcher puts a +1/+1 counter on itself
5. Vaultborn Tyrant — When Vaultborn Tyrant gains life, Blood Researcher puts a +1/+1 counter on itself
6. Prosperous Innkeeper — When Prosperous Innkeeper gains life, Blood Researcher puts a +1/+1 counter on itself
7. Essence Warden — When Essence Warden gains life, Blood Researcher puts a +1/+1 counter on itself
8. Virulent Emissary — When Virulent Emissary gains life, Blood Researcher puts a +1/+1 counter on itself
9. Bogwater Lumaret — When Bogwater Lumaret gains life, Blood Researcher puts a +1/+1 counter on itself
10. Social Climber — When Social Climber gains life, Blood Researcher puts a +1/+1 counter on itself

2,066 other cards cause it too. These are the ones with the most connections.

a creature gets a counter — 2,691 cards in the game can cause this (Blood Researcher is one).

When Blood Researcher gets a counter:

1. Hollowmurk Siege — draws you 1 card
2. Ant-Man, Colony Commander — makes a token
3. Earth Kingdom General — gains you that much life
4. Casey Jones, Back Alley Brute — deals that much damage
5. Generous Patron — draws you 1 card
6. Shalai and Hallar — deals that much damage
7. Danny Pink — draws you 1 card
8. Enduring Scalelord — puts a +1/+1 counter on itself
9. Bold Plagiarist — puts counters on a permanent
10. Mikey & Leo, Chaos & Order — draws you 1 card

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

anything gets a counter — 4,415 cards in the game can cause this (Blood Researcher is one).

1. All Will Be One — When Blood Researcher gets a counter, All Will Be One deals that much damage

8 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 (Blood Researcher is one).

When Blood Researcher 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

113 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 (Blood Researcher is one).

When Blood Researcher 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 (Blood Researcher is one).

When Blood Researcher blocks:

1. Mage Hunters' Onslaught — makes a player lose 1 life
2. Carnage Gladiator — makes a player lose 1 life
3. Tide of War — sacrifices a creature
4. Dead-Iron Sledge — kills a creature
5. Dwindle — kills a creature
6. Shield of the Righteous — triggers

22 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 (Blood Researcher is one).

When Blood Researcher attacks:

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

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

When Blood Researcher enters:

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

305 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 (Blood Researcher is one).

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

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