Waker of the Wilds — ruling 1

The land-animation effect lasts indefinitely. It doesn’t wear off during the cleanup step or when you lose control of Waker of the Wilds.

Waker of the Wilds — ruling 2

If the ability targets a land that’s already a creature, that land creature’s base power and toughness will become 0/0, overwriting its previous base power and toughness. Other effects that modify its power and/or toughness (including any +1/+1 counters that were on it) will continue to apply.

Waker of the Wilds : règles, fonctionnement et interactions (MTG)

Waker of the Wilds is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Put X +1/+1 counters on target land you control. That land becomes a 0/0 Elemental creature with haste. It's still a land.

How it works : Waker of the Wilds

Original English text — Wizards of the Coast / Scryfall

#1September 29, 2017· Wizards of the Coast
The land-animation effect lasts indefinitely. It doesn’t wear off during the cleanup step or when you lose control of Waker of the Wilds.
No other card is named in this ruling.
#2September 29, 2017· Wizards of the Coast
If the ability targets a land that’s already a creature, that land creature’s base power and toughness will become 0/0, overwriting its previous base power and toughness. Other effects that modify its power and/or toughness (including any +1/+1 counters that were on it) will continue to apply.
No other card is named in this ruling.