Cheapest priced copy (Ravnica: City of Guilds): $0.35 at Card Kingdom, near mint, their price list as of .
Terraformer 
Creature — Human Wizard · 2/2 · Common · Ravnica: City of Guilds · #70
{1}: Choose a basic land type. Each land you control becomes that type until end of turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica: City of Guilds | 70 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 1 October 2005Terraformer’s effect overwrites the land type of all lands you control that had other types and gives a land type to all lands you control that don’t normally have one.
- 1 October 2005Changing a land’s type doesn’t change its name or whether it’s legendary or basic.
- 1 October 2005Lands you control will have the mana ability of the basic land type you choose (for example, Forests can tap to produce green mana) and will lose all other innate abilities they had.