Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Teval, the Balanced Scale

Flying
Whenever Teval attacks, mill three cards. Then you may return a land card from your graveyard to the battlefield tapped.
Whenever one or more cards leave your graveyard, create a 2/2 black Zombie Druid creature token.

Sol Ring

Gilt-Leaf Archdruid

Whenever you cast a Druid spell, you may draw a card.
Tap seven untapped Druids you control: Gain control of all lands target player controls.

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Seton, Krosan Protector

Tap an untapped Druid you control: Add {G}.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.