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.

Magic Online Promos

Archenemy: Nicol Bolas

+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 your library. Those lands become 4/4 Elemental creatures with trample. They're still lands.

Magic 2015

San Diego Comic-Con 2014

If the land targeted by the first ability entered the battlefield this turn, it won’t be able to attack and its activated abilities with {T} in the cost (including its mana ability) can’t be activated (unless something gives it haste). The same is true for the lands put onto the battlefield with the third ability.

The type-changing effects of the first and third abilities don’t have a duration. They last indefinitely.