Nissa, Worldwaker

+1: Target land you control becomes a 4/4 Elemental creature with trample. It's still a land.
+1: Untap up to four target Forests.
−7: Search your library for any number of basic land cards, put them onto the battlefield, then shuffle. Those lands become 4/4 Elemental creatures with trample. They're still lands.

Counterspell

Dark Depths

Dark Depths enters the battlefield with ten ice counters on it.
{3}: Remove an ice counter from Dark Depths.
When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Foresee

Mana Geyser

Add {R} for each tapped land your opponents control.

Yavimaya, Cradle of Growth

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

Nissa, Who Shakes the World

Whenever you tap a Forest for mana, add an additional {G}.
+1: Put three +1/+1 counters on up to one target noncreature land you control. Untap it. It becomes a 0/0 Elemental creature with vigilance and haste that's still a land.
−8: You get an emblem with "Lands you control have indestructible." Search your library for any number of Forest cards, put them onto the battlefield tapped, then shuffle.

Jace, Arcane Strategist

Whenever you draw your second card each turn, put a +1/+1 counter on target creature you control.
+1: Draw a card.
−7: Creatures you control can't be blocked this turn.

Chandra, Flame's Catalyst

+1: Chandra, Flame's Catalyst deals 3 damage to each opponent.
−2: You may cast target red instant or sorcery card from your graveyard. If that spell would be put into your graveyard, exile it instead.
−8: Discard your hand, then draw seven cards. Until end of turn, you may cast spells from your hand without paying their mana costs.

Omnath, Locus of Mana

You don't lose unspent green mana as steps and phases end.
Omnath, Locus of Mana gets +1/+1 for each unspent green mana you have.

Overlaid Terrain

As Overlaid Terrain enters the battlefield, sacrifice all lands you control.
Lands you control have "{T}: Add two mana of any one color."

Doubling Cube

{3}, {T}: Double the amount of each type of unspent mana you have.

Forest

Wall of Stone

Copy Artifact

You may have Copy Artifact enter the battlefield as a copy of any artifact on the battlefield, except it's an enchantment in addition to its other types.

Splendid Reclamation

Return all land cards from your graveyard to the battlefield tapped.

Library of Leng

You have no maximum hand size.
If an effect causes you to discard a card, discard it, but you may put it on top of your library instead of into your graveyard.

Fork

Copy target instant or sorcery spell, except that the copy is red. You may choose new targets for the copy.

Mana Short

Tap all lands target player controls and that player loses all unspent mana.

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

Swamp

Mountain

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Wrenn and Six

+1: Return up to one target land card from your graveyard to your hand.
−1: Wrenn and Six deals 1 damage to any target.
−7: You get an emblem with "Instant and sorcery cards in your graveyard have retrace." (You may cast instant and sorcery cards from your graveyard by discarding a land card in addition to paying their other costs.)

Enter the Infinite

Draw cards equal to the number of cards in your library, then put a card from your hand on top of your library. You have no maximum hand size until your next turn.