Focus on consistency: If your deck struggles to draw the right cards, consider adding more copies of the necessary cards (you can have up to four copies of non-Energy cards in a deck)
Banlist History Restriction changes recorded for Subterror Behemoth Umastryx
D-END, which has similar effects, is more senior, but since X doesn't specify materials, it's a card that can be used in a variety of Decks
Removal I leaned towards creature cards for much of my removal suite to keep up synergies with my game plan, but sometimes youll want faster interaction (like Swords to Plowshares) or bigger effects (like the awesome Exterminatus)
Track every card you own, regular and foil variants, quantities, and languages
It's also very common for HERO players to use Mirror Force to protect Dark Law from battle since his effect banishes all the attacking monsters, stopping any effects that may activate in the graveyard (which are rather common in Yugioh)