Urborg, Tomb of Yawgmoth

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

Nylea's Presence

Enchant land
When this Aura enters, draw a card.
Enchanted land is every basic land type in addition to its other types.

Shadow Prophecy

Domain — Look at the top X cards of your library, where X is the number of basic land types among lands you control. Put up to two of them into your hand and the rest into your graveyard. You lose 2 life.

Prismatic Geoscope

This artifact enters tapped.
Domain — {T}: Add X mana in any combination of colors, where X is the number of basic land types among lands you control.

Prismatic Omen

Lands you control are every basic land type in addition to their other types.

Yavimaya, Cradle of Growth

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

Scion of Draco

Domain — This spell costs {2} less to cast for each basic land type among lands you control.
Flying
Each creature you control has vigilance if it's white, hexproof if it's blue, lifelink if it's black, first strike if it's red, and trample if it's green.

Jared Carthalion

+1: Create a 3/3 Kavu creature token with trample that's all colors.
−3: Choose up to two target creatures. For each of them, put a number of +1/+1 counters on it equal to the number of colors it is.
−6: Return target multicolored card from your graveyard to your hand. If that card was all colors, draw a card and create two Treasure tokens.
Jared Carthalion can be your commander.

Worldly Counsel

Domain — Look at the top X cards of your library, where X is the number of basic land types among lands you control. Put one of those cards into your hand and the rest on the bottom of your library in any order.

Drag to the Bottom

Domain — Each creature gets -X/-X until end of turn, where X is 1 plus the number of basic land types among lands you control.

Gaea's Balance

As an additional cost to cast this spell, sacrifice five lands.
Search your library for a land card of each basic land type, put those cards onto the battlefield, then shuffle.

Valakut, the Molten Pinnacle

This land enters tapped.
Whenever a Mountain you control enters, if you control at least five other Mountains, you may have this land deal 3 damage to any target.
{T}: Add {R}.

Planar Despair

Domain — All creatures get -1/-1 until end of turn for each basic land type among lands you control.

Dryad of the Ilysian Grove

You may play an additional land on each of your turns.
Lands you control are every basic land type in addition to their other types.