Molderhulk

Undergrowth — This spell costs {1} less to cast for each creature card in your graveyard.
When Molderhulk enters, return target land card from your graveyard to the battlefield.

Pitiless Gorgon

Spinal Centipede

When Spinal Centipede dies, put a +1/+1 counter on target creature you control.

Lotleth Giant

Undergrowth — When Lotleth Giant enters, it deals 1 damage to target opponent for each creature card in your graveyard.

Swamp

Forest

Moodmark Painter

Undergrowth — When Moodmark Painter enters, target creature gains menace and gets +X/+0 until end of turn, where X is the number of creature cards in your graveyard. (It can't be blocked except by two or more creatures.)

Undercity's Embrace

Target opponent sacrifices a creature of their choice. If you control a creature with power 4 or greater, you gain 4 life.

Erstwhile Trooper

Discard a creature card: Erstwhile Trooper gets +2/+2 and gains trample until end of turn. Activate only once each turn.

Vigorspore Wurm

Undergrowth — When Vigorspore Wurm enters, target creature gains vigilance and gets +X/+X until end of turn, where X is the number of creature cards in your graveyard.
Vigorspore Wurm can't be blocked by more than one creature.

Rhizome Lurcher

Undergrowth — Rhizome Lurcher enters with a number of +1/+1 counters on it equal to the number of creature cards in your graveyard.

Kraul Foragers

Undergrowth — When Kraul Foragers enters, you gain 1 life for each creature card in your graveyard.