Floodgate is an unofficial term for a card with a continuous effect that restricts one or both players from performing some action. Most notable floodgates are Continuous Trap Cards, though some come in the form of Spell Cards (e.g. "Necrovalley", "Dimensional Fissure") or monsters (e.g. "Majesty's Fiend", "Vanity's Fiend"). Floodgates tend to see widespread play due to their ability to paralyze an opponent's Deck if protected and generally are used as Side Deck Cards.
They are better used in Decks that can afford them with little or no drawback. Examples include:
- "Yosenju" Decks making use of "Vanity's Emptiness", "Lose 1 Turn" and "Macro Cosmos"/"Dimensional Fissure", since they generally revolve around a string of Normal Summons of the Level 4 "Yosenju" monsters rather than Special Summoning them, which in turn will return to the hand at the End Phase.
- "Sylvan" Decks using "Mistake", since the Deck generally doesn't need any search effect, placing the needed cards on the top of the Deck in order to Excavate them.
- Any Deck that relies on only one Attribute can afford using "Gozen Match" and any Deck that relies on only one Type can use "Rivalry of Warlords", etc.