Jodah's Codex
Artifact
Domain — , 
: Draw a card. This ability costs 
less to activate for each basic land type among lands you control.
"If you remember nothing else of our world's history, remember this: Phyrexians can be defeated." —Jodah
Aaron Miller
Dominaria United (DMU)
• #233Rulings
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.
(wotc • 2022-09-09)
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.
(wotc • 2022-09-09)
Rulings
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.
(wotc • 2022-09-09)
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.
(wotc • 2022-09-09)