Draco

Domain — This spell costs {2} less to cast for each basic land type among lands you control.
Flying
Domain — At the beginning of your upkeep, sacrifice this creature unless you pay {10}. This cost is reduced by {2} for each basic land type among lands you control.

The List

From the Vault: Dragons

Draco costs {2} less to play for each basic land type among lands you control.
Flying
At the beginning of your upkeep, sacrifice Draco unless you pay {10}. This cost is reduced by {2} for each basic land type among lands you control.

Planeshift

Draco costs o2 less to play for each basic land type among lands you control.
Flying
At the beginning of your upkeep, sacrifice Draco unless you pay o10. This cost is reduced by o2 for each basic land type among lands you control.

The 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.

Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.