Mermail Abyssbalaen

The monster effect "During your Main Phase: You can discard 4 'Mermail' monsters from your hand to the Graveyard; Special Summon this card from your hand" is an Ignition Effect that activates in the hand. (It does not target. When activating this effect, you discard 4 "Mermail" monsters from your hand to the Graveyard as the cost.)

The monster effect "When Special Summoned by this effect: This card gains 500 ATK, then you can destroy cards your opponent controls up to the number of 'Mermail' monsters in your Graveyard" is a Trigger Effect.

The monster effect "This card gains 500 ATK, then you can destroy cards your opponent controls up to the number of 'Mermail' monsters in your Graveyard" is an effect that targets any number of cards on your opponent's field (from 1 up to the number of "Mermail" monsters in your Graveyard).

The resolution of "This card gains 500 ATK" and the resolution of "destroy cards your opponent controls up to the number of 'Mermail' monsters in your Graveyard" are treated as occurring simultaneously.

The monster effect "You can Tribute 1 other face-up Attack Position 'Mermail' monster; if this card attacks a Defense Position monster, inflict piercing battle damage to your opponent" is an Ignition Effect. (It does not target. When activating this effect, you Tribute 1 face-up Attack Position "Mermail" monster you control as the cost.)