Effect
You can Tribute this card and 1 Sea Serpent-Type monster; Special Summon 1 "Poseidra, the Atlantean Dragon" from your hand or Deck, then all monsters your opponent currently controls lose 300 ATK.
This card is treated as an "Atlantean" monster.
The monster effect of "Poseidra, the Atlantean Dragon Lord" is an Ignition Effect. (It does not target.)
When activating the effect, you must Tribute 2 monsters as cost: the "Poseidra, the Atlantean Dragon Lord" activating the effect itself, and 1 Sea Serpent-Type monster you control. (You can also Tribute a face-down Defense Position Sea Serpent-Type monster you control.)
You can activate the monster effect of "Poseidra, the Atlantean Dragon Lord" even if there are no face-up monsters in your opponent's Monster Zone.
The effect "Special Summon 1 'Poseidra, the Atlantean Dragon Lord' from your hand or Deck" and the effect "then, all face-up monsters your opponent controls lose 300 ATK" are not treated as occurring simultaneously. (If there are no face-up monsters in your opponent's Monster Zone when the effect resolves, the effect finishes resolving after the "Special Summon 1 'Poseidra, the Atlantean Dragon Lord' from your hand or Deck" part.)
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