Forest

a Forest enters the battlefield — 85 cards in the game can cause this (Forest is one).

1. Titania, Nature's Force — When Forest enters, Titania, Nature's Force makes a token
2. Baru, Fist of Krosa — When Forest enters, Baru, Fist of Krosa gives +1/+1
3. Reach of Branches — When Forest enters, Reach of Branches returns itself from the graveyard
4. Tourach's Chant — When Forest enters, Tourach's Chant deals 3 damage
5. Battlewand Oak — When Forest enters, Battlewand Oak gets +2/+2
6. Staff of the Wild Magus — When Forest enters, Staff of the Wild Magus gains you 1 life
7. Necklace of Girion — When Forest enters, Necklace of Girion puts a counter on a creature
8. Roiling Canopy — When Forest enters, Roiling Canopy gives +3/+3

a land enters the battlefield — 1,560 cards in the game can cause this (Forest is one).

1. Primeval Bounty — When Forest enters, Primeval Bounty gains you 3 life
2. Toph, Earthbending Master — When Forest enters, Toph, Earthbending Master puts a counter on a permanent
3. Dancing from Dark to Dawn — When Forest enters, Dancing from Dark to Dawn makes a token
4. Emeria Shepherd — When Forest enters, Emeria Shepherd brings a card back
5. Quest for the Necropolis — When Forest enters, Quest for the Necropolis puts a quest counter on itself
6. Soul Stair Expedition — When Forest enters, Soul Stair Expedition puts a quest counter on itself
7. Nissa of Shadowed Boughs — When Forest enters, Nissa of Shadowed Boughs puts counters on a permanent
8. Thranduil, Sindarin Liege // Silvan Rally — When Forest enters, Thranduil, Sindarin Liege // Silvan Rally makes a token
9. Silvan Reveler — When Forest enters, Silvan Reveler returns itself from the graveyard
10. Floral Evoker — When Forest enters, Floral Evoker puts a +1/+1 counter on itself

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