Fetchlands are the next piece of the puzzle, and I advocate for running at the very least Arid Mesa, Fabled Passage, Prismatic Vista and then one of Windswept Heath/Marsh Flats/Bloodstained Mire etc
C Common Psychic Eraser Laser X SPELL Send 1 monster your opponent controls that was Special Summoned from the Extra Deck to the GY, then your opponent gains LP equal to the original ATK or DEF of that monster (whichever is higher)
Hydras usually appear at rare and are at least Limited bomb tier with a lot of them seeing Constructed play
This multiplayer format is quite possibly the most unique compared to the other formats the game provides, featuring larger deck sizes, higher life totals, and more players to interact with in a given game
When you have such a high number of existing mechanics, I can imagine that coming up with something both new and fun is very hard