Unclaimed Territory
Land
As this land enters, choose a creature type.
: Add 
.
: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.
Dimitar Marinski
Rulings
To choose a creature type, you must choose an existing creature type, such as Vampire or Knight. You can't choose multiple creature types, such as "Vampire Knight." Card types such as artifact can't be chosen, nor can subtypes that aren't creature types, such as Jace, Vehicle, or Treasure.
(wotc • 2018-01-19)
Printings
Rulings
To choose a creature type, you must choose an existing creature type, such as Vampire or Knight. You can't choose multiple creature types, such as "Vampire Knight." Card types such as artifact can't be chosen, nor can subtypes that aren't creature types, such as Jace, Vehicle, or Treasure.
(wotc • 2018-01-19)