If I don't have any Digimon with [Seadramon], and use this card's effect to play a Digimon card Seadramon] in its name from the digivolution cards of one of my blue Digimon, does the effect to "return 1 of your opponent's level 4 or lower Digimon to the bottom of its owner's deck" activate?

Yes, the effect will activate since a Digimon with [Seadramon] was played earlier.

Maelstrom rulings (BT11-098)

1 official ruling from Bandai, last ruled Mar 28, 2024. Straight answers to how this card actually resolves.

Effect: [Main] You may play 1 blue Digimon card from one of your blue Digimon's digivolution cards without paying the cost. Then, if you have a Digimon with [Seadramon] in its name in play, return 1 of your opponent's level 4 or lower Digimon to the bottom of its owner's deck.
Security effect: [Security] Activate this card's [Main] effects.

Official Q&A

If I don't have any Digimon with [Seadramon], and use this card's effect to play a Digimon card Seadramon] in its name from the digivolution cards of one of my blue Digimon, does the effect to "return 1 of your opponent's level 4 or lower Digimon to the bottom of its owner's deck" activate?
Yes, the effect will activate since a Digimon with [Seadramon] was played earlier.
Ruled Mar 28, 2024

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Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.

Maelstrom rulings (BT11-098)

1 official ruling from Bandai, last ruled Mar 28, 2024. Straight answers to how this card actually resolves.

Effect: [Main] You may play 1 blue Digimon card from one of your blue Digimon's digivolution cards without paying the cost. Then, if you have a Digimon with [Seadramon] in its name in play, return 1 of your opponent's level 4 or lower Digimon to the bottom of its owner's deck.
Security effect: [Security] Activate this card's [Main] effects.

Official Q&A

If I don't have any Digimon with [Seadramon], and use this card's effect to play a Digimon card Seadramon] in its name from the digivolution cards of one of my blue Digimon, does the effect to "return 1 of your opponent's level 4 or lower Digimon to the bottom of its owner's deck" activate?
Yes, the effect will activate since a Digimon with [Seadramon] was played earlier.
Ruled Mar 28, 2024

Got a line that uses Maelstrom? Map it in the builder and share it with a link.