Flying
Domain — Aven Trailblazer's toughness is equal to the number of basic land types among lands you control.
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.
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.
Aven Trailblazer’s second ability is a “characteristic-defining ability.” It applies at all times in all zones.