If Leyline of Combustion is in your opening hand, you may begin the game with it on the battlefield.
Whenever you and/or at least one permanent you control becomes the target of a spell or ability an opponent controls, Leyline of Combustion deals 2 damage to that player.
A player's "opening hand" is the hand of cards the player has after all players have taken mulligans. If players have any cards in hand that allow actions to be taken with them from a player's opening hand, the starting player takes all such actions first in any order, followed by each other player in turn order. Then the first turn begins.
12-07-2019
wotc
Leyline of Combustion's triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
12-07-2019
wotc
If a spell targets you and/or a permanent you control multiple times, or if a spell targets you and one or more permanents you control, Leyline of Combustion's triggered ability triggers once.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.