Touchstone

an artifact becomes tapped — 88 cards in the game can cause this (Touchstone is one).

When an artifact becomes tapped thanks to Touchstone:

1. Powerleech — gains you 1 life
2. Artifact Possession — deals 2 damage
3. Haunting Wind — deals 1 damage
4. Relic Putrescence — puts a counter on a permanent
5. Relic Bind — triggers

an artifact is cast — 3,683 cards in the game can cause this (Touchstone is one).

When Touchstone is cast:

1. Master Pakku — gets +1/+1
2. Mendicant Core, Guidelight — copies a spell
3. Sai, Master Thopterist — makes a token
4. Ravenous Robots — makes a token
5. Pinnacle Emissary — makes a token
6. Mirrodin Besieged — makes a token
7. Poetic Ingenuity — makes a token
8. Digsite Engineer — makes a token
9. Myrsmith — makes a token
10. Dr. Madison Li — puts a counter on a permanent you control

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

a nontoken artifact enters the battlefield — 3,768 cards in the game can cause this (Touchstone is one).

When Touchstone enters:

1. Ultron, Artificial Malevolence — makes a token
2. The Prydwen, Steel Flagship — makes a token
3. Conquest Mission — puts a quest counter on itself
4. Surge Conductor — proliferates
5. Replication Specialist — makes a token
6. Weapons Manufacturing — makes a token
7. Mirrorworks — makes a token

an artifact enters the battlefield — 4,643 cards in the game can cause this (Touchstone is one).

When Touchstone enters:

1. Transplant Theorist — draws you 1 card
2. Elvish Archivist — puts 2 +1/+1 counters on itself
3. Golbez, Crystal Collector — surveils
4. Sludge Strider — makes a player lose 1 life
5. Underhanded Designs — makes each opponent lose 1 life
6. Mechan Assembler — makes a token
7. Glassdust Hulk — gets +1/+1
8. Rook Turret — draws you 1 card
9. Hedron Detonator — deals 1 damage
10. Pactdoll Terror — makes each opponent lose 1 life

55 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 (Touchstone is one).

When Touchstone enters:

1. HYDRA Assault Robot — deals 1 damage
2. Era of Innovation — puts a counter on a permanent you control

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

anything is cast — 31,128 cards in the game can cause this (Touchstone is one).

When Touchstone is cast:

1. Sokka, Bold Boomeranger — puts a +1/+1 counter on itself
2. Saheeli, Radiant Creator — puts a counter on a permanent you control

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