Cheapest priced copy (Ixalan): $0.49 at Card Kingdom, near mint, their price list as of .
Waker of the Wilds 
Creature — Merfolk Shaman · 3/3 · Rare · Ixalan · #215
{X}{G}{G}: 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.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ixalan Promos | 215s | Rare | — | $0.59 |
| Ixalan | 215 | Rare | $0.49 | $0.79 |
| Zendikar Rising Commander | 86 | Rare | $0.49 | — |
2 rulings from Wizards of the Coast
- 29 September 2017If 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.
- 29 September 2017The land-animation effect lasts indefinitely. It doesn’t wear off during the cleanup step or when you lose control of Waker of the Wilds.