Once the triggered ability has triggered once during a turn, it can't trigger again, even if the triggered ability is still on the stack, has been countered, or has otherwise left the stack
Mount Doom is a legendary land card that acts as a mana fixer for black-red decks, while also bringing two remarkable new effects to the table
The Hydreigon can serve as catcher bait for the Garchomp/Altaria player
Legendary Land Land (CTRL to add secondary) protection Swiftfoot Boots Equipped creature has hexproof and haste
The goal here is to Fusion, Synchro, Xyz, Pendulum, and Link summon the game-ending cards quickly, and if you're lucky with your first hand, you can finish it before the enemy has a turn
Thats part of why an overloaded Cyclonic Rift is so good