Exploding Borders — ruling 1

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.

Exploding Borders — ruling 2

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.

Exploding Borders — ruling 3

You do what the spell says in order, so you'll put a new basic land card onto the battlefield before you determine the value of X.

Exploding Borders — ruling 4

Exploding Borders will still deal damage even if you don't put a land card onto the battlefield.

Exploding Borders — ruling 5

Exploding Borders has only one target: the player. If that player becomes an illegal target by the time Exploding Borders would resolve, the entire spell doesn't resolve. You won't get to search for a basic land card.

Exploding Borders : règles, fonctionnement et interactions (MTG)

Exploding Borders is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Domain — Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle. Exploding Borders deals X damage to target player or planeswalker, where X is the number of basic land types among lands you control.

How it works : Exploding Borders

Original English text — Wizards of the Coast / Scryfall

#1June 18, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#2June 18, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#3February 1, 2009· Wizards of the Coast
You do what the spell says in order, so you'll put a new basic land card onto the battlefield before you determine the value of X.
No other card is named in this ruling.
#4February 1, 2009· Wizards of the Coast
Exploding Borders will still deal damage even if you don't put a land card onto the battlefield.
No other card is named in this ruling.
#5February 1, 2009· Wizards of the Coast
Exploding Borders has only one target: the player. If that player becomes an illegal target by the time Exploding Borders would resolve, the entire spell doesn't resolve. You won't get to search for a basic land card.
No other card is named in this ruling.