That opponent may choose to put all of the cards into one pile and leave the other pile empty. In that case, the ability’s controller chooses whether to put the revealed cards into their hand or into their graveyard.

The player who controls the triggered ability chooses which opponent separates the cards into two piles. This choice is made after revealing those cards.

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.