You can discard 2 other WATER monsters to the Graveyard; Special Summon this card from your hand. When you do: You can add 1 "Abyss-" Spell/Trap Card from your Deck to your hand. You can Tribute 1 other face-up Attack Position WATER monster; this card can make a second attack during each Battle Phase this turn.
Can be Special Summoned from your Hand, by discarding 2 WATER monsters from your Hand to the Graveyard.
Can add 1 “Abyss-” Spell/Trap from the Deck to your Hand.
Strong ATK and DEF stats.
Requires 2 Tribute materials to Tribute Summon.
Discarding 2 WATER monsters is quite costly and you might lose card advantage.
Together with Abyss Soldier and Abyss Warrior, they form a synergy that relies on discarding cards, and effects that activate from the Graveyard when discarded, to gain card advantage and Field advantage simultaneously.
On top of that, they can utilize Sea Stealth Attack as a deadly weapon to decimate your opponent’s monsters and exhaust their protection resources.
These are the archetype monsters that are able to synergize well with each other. Mermail Abysspike has effects that activate when it was Normal or Special Summoned, which allows you to discard 1 WATER monster to the Graveyard and add 1 Level 3 WATER monster from your Deck to your hand. Mermail Abyssleed allows you to discard 3 other WATER monsters to the Graveyard and Special Summon this monster your hand, and target 1 "Abyss-" Spell/Trap Card in your Graveyard; add that target to your hand.
Additionally, you can Tribute 1 other face-up Attack Position "Mermail" monster; send 1 random card from your opponent's hand to the Graveyard. Mermail Abyssturge allows you to discard 1 WATER monster to the Graveyard, then target 1 Level 3 or lower WATER monster in your Graveyard, add that target to your hand.
When you discard Mermail Abyssgunde to the Graveyard, you can target 1 "Mermail" monster in your Graveyard, except "Mermail Abyssgunde", Special Summon that target. When you discard Mermail Abysshilde to the Graveyard, you can Special Summon 1 "Mermail" monster from your hand, except "Mermail Abysshilde".
Mermail Mermail Abyssbalaen allows you to discard 4 other "Mermail" monsters to the Graveyard and then Special Summon this card from your hand. When you do, you can target cards your opponent controls, up to the number of "Mermail" monsters in your Graveyard (if possible); this card gains 500 ATK, and if it does, destroy those targets (if any).
Additionally, you can Tribute 1 other face-up Attack Position "Mermail" monster; this card is able to destroy a defense position monster at the start of the Damage Step. When Mermail Abyssnose destroys an opponent's monster by battle and sends it to the Graveyard, you can discard 1 WATER monster to the Graveyard in order to Special Summon 1 "Mermail" monster from your Deck in face-up Defense Position.
Abyss-scale of the Kraken can be equipped to a "Mermail" monster to gain 400 ATK. You can negate a monster effect that was activated on your opponent's side of the field, and then send this card to the Graveyard.
Abyss-squall can target 3 "Mermail" monsters in your Graveyard; Special Summon those targets in face-up Defense Position, however their effects are negated and they cannot declare an attack, and they will be destroyed during the End Phase.
A Legendary Ocean increases all WATER monsters’ ATK and DEF stats by 200, while reducing the level of the monsters by 1, so you can Tribute summon Mermail Abyssmegalo with 1 less tribute.
Sea Stealth Attack grants your Mermail Abyssmegalo the ability to destroy your opponent’s monster during the start of Damage Step, and can banish your WATER monster to either protect them, or your face-up Spell/Trap cards from destruction.
Citadel Whale can be discarded to the Graveyard as 1 of the cost to Special Summon Mermail Abyssmegalo, because you can Special Summon Citadel Whale from the Graveyard to the Field, by tributing 2 other WATER monsters.