Cheapest priced copy (Duel Decks: Phyrexia vs. the Coalition): $0.35 at Card Kingdom, near mint, their price list as of .
Power Armor 
Artifact · Uncommon · Invasion · #309
Domain — {3}, {T}: Target creature gets +1/+1 until end of turn for each basic land type among lands you control.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $0.35 to $4.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Phyrexia vs. the Coalition | 62 | Uncommon | $0.35 | — |
| Invasion | 309 | Uncommon | $0.35 | $4.99Out of stock |
| The List | INV-309 | Uncommon | $0.35 | — |
2 rulings from Wizards of the Coast
- 18 June 2021The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don't contribute to domain abilities.
- 18 June 2021Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.