Mermail

"Mermail" ( Māmeiru) is an archetype of WATER-Attribute and Aqua, Fish and Sea Serpent-Type monsters, introduced in the Abyss Rising. They are based on mermaids outfitted with armor, hence "mail". They are intimately related to the "Abyss-" archetype, as they all belong to the archetype. Level 3 "Mermail" are all Aqua-Type female monsters, Level 4 "Mermail" are all Fish-Type male monsters, and Level 7 "Mermail" are all Sea Serpent-Type monsters, except for Mermail Abyssteus, which is an Aqua-Type monster.

Each "Mermail" monster is based on a real life aquatic animal. The original three female "Mermail" monsters released in Abyss Rising, Mermail Abysslinde, Mermail Abyssgunde and Mermail Abysshilde, have names coming from the Rhinemaidens (Woglinde, Wellgunde, Flosshilde) in the German opera Der Ring des Nibelungen (The Ring of the Nibelung) by Richard Wagner. The Level 7 "Mermail" monsters, Mermail Abyssmegalo, Mermail Abyssleed and Mermail Abyssteus take inspiration from extinct aquatic species. The Xyz Monsters, Mermail Abyssgaios and Mermail Abysstrite take inspiration from Ancient Greek deities.

Playing Style
Level 3 "Mermail" monsters all share a similar effect when they get sent to the Graveyard - they Special Summon another "Mermail", letting them swarm the field. The Level 4 "Mermail" monsters can activate their effects when they are Normal or Special Summoned, by discarding a WATER monster from your Hand, which will trigger the effect of the previous monsters effects, and the Level 4 monsters help to either search the Deck or graveyard for a Level 3 WATER monster. The higher-Level "Mermails" can Special Summon themselves with relative-ease by sending other "Mermails" to the Graveyard, which will also trigger their effects. The "boss" monster of the archetype, "Mermail Abyssgaios", is a powerful control card, with 2 effects that forces your opponent into a corner, either by preventing their most powerful monsters from attacking and/or by negating their weaker monsters' effects.

They have a small relation to the "Umi" series, since one of their support cards, "Abyss-strom," uses "Umi" for its effect. This is also evident in the new Field Spell introduced in their debut set of Abyss Rising (which, namewise, partially refers to them as well) whose effect treats it as "Umi." The Field Spell, Lemuria, the Forgotten City, helps them Xyz for higher Rank Xyz Monsters, and partially supports the Summoning of "Abyssgaios". Combining the original "Umi" cards with these newer cards is not a good option, since there are much better options available for this task which outclass the Umi cards. The "Umi" cards only have 1 connection in which they function properly, and their effects are generally weaker than those of the "Mermail". Another possibility for a field spell is "Clear World". It causes the user of a water monster to discard at the end of their phase, facilitating their effects, while possibly hindering the other player.

Swarming and Xyz Summon is thus their main style of play, and with all the recent support for WATER-attribute monsters, can do a decent job of Summoning Xyz Monsters. By utilizing support they can reach from Rank 3 ("Number 17: Leviathan Dragon" and "Black Ray Lancer") to Rank 9 ("Number 9: Dyson Sphere"). With 2 "Abyssmegalo" and "Lemuria, the Forgotten City" they can make Rank 9 fairly easily. Rank 4 is accessible with just the Level 4 monsters themselves. Rank 5 is created with Lemuria, the Forgotten City and 2 Level 3 monsters, while 6 is reached with 2 Level 4 monsters and Lemuria. Rank 7 is reached plainly by 2 "Mermail Abyssmegalo" without help from Lemuria. Rank 8 is impossible without 3 Level 5 monsters, 4 Level 4 monsters or 5 Level 3 Monsters, all of which seem like a waste of cards to spend on what's currently available at this Rank.

Another strategy is to lock the attacks and effects of strong opponent monsters with Mermail Abyssgaios, using his effect to negate the effect of face-up enemy monsters, as his effect can be activated in any player's turn. To Summon him, one can Special Summon Mermail Abyssmegalo's own effect, and then adding Abyss-sphere to your hand, letting you Summon another Megaloabyss in your next turn. This can also be done with Mermail Abysslinde's effect to Summon Megaloabyss from your Deck. Using the effect of Lemuria, the Forgotten City and the swarming power of Mermails can help as well, needing 3 face-up Level 4 Mermails or 4 face-up Level 3 Mermails.

"Mermail Abysslinde" is one of the Deck's most important Summoning cards. It acts as a "Mother Grizzly" for Mermails that also works upon being destroyed by card effects.

Mermails also go hand-in-hand with the "Atlantean" archetype since their effects are activated when sent to the graveyard to activate a WATER monsters effect. By discarding "Atlantean Heavy Infantry", "Atlantean Marksman", or "Atlantean Dragoons", to activate the Mermails effects you can destroy a card on the field (Heavy Infantry and Marksman) or search your Deck for any Sea Serpent type monster (Dragoons), such as Megaloabyss, while also gaining the Mermail's effects.

Weaknesses
"Thunder King Rai-Oh" severely slows down this Deck theme as it halts all of the searching effects of "Mermail" monsters while also being a higher ATK than most of them as well. "Deck Lockdown" also works and stops Special Summoning from the Main Deck too, but can be more easily countered so it is more useful as an early disruption tactic and for Tribute-themed and/or Synchro/XYZ monster focused Decks that have no need to Special Summon from the Main Deck at all.

"Debunk", "Forbidden Graveyard", "Necrovalley", "The End of Anubis" and "Soul Drain" also halts many of the key monster effects of a Mermail Deck as well to slow it down, but it does not affect the Xyz Summon options available unlike "Thunder King Rai-Oh". "Skill Drain" also affects the speed of this Deck and can assist in slowing it down too, but without "Debunk" or "Soul Drain" (or other similar graveyard negation effect cards) their graveyard activating effects are not affected and can result in its destruction.

Banish effect cards can cause havoc on "Mermail" and "Mermail"/"Abyss" Decks because they lose their graveyard activating effects, so "Macro Cosmos" and "Dimensional Fissure" are worth consideration. It also can prevent "Moulinglacia the Elemental Lord" from being Summoned through a lack of WATER monsters in the Graveyard.

"Bottomless Trap Hole" is also a good option for removing dangerous support, such as "Moulinglacia the Elemental Lord", "Mermail Abyssmegalo" and "Mermail Abysslinde". And while "King Tiger Wanghu" can disrupt a "Mermail" or "Mermail"/"Abyss" Deck, its continuous destruction effect will trigger their own effects normally, so cautious use is required: "Fossil Dyna Pachycephalo" the "Vanity's" monsters, "Vanity's Emptiness" and "Jowgen the Spiritualist" may be a more effective option in countering "Mermail"s.

"Magical Thorn" can be an anomalous choice against "Mermails" as many of their effects rely on discarding cards. "Elemental HERO Inferno" can also be another outlandish choice because many of them fall to this card's effect by itself unless "Abyss-scorn" is used on one of the stronger "Mermails".

One major problem a "Mermail" user might face is "over-extending". Because so many Mermail effects rely on discarding or being discarded, a Duelist using the archetype might spend all but a couple of cards in their hand on swarming the field with monsters. Despite the many searchers of the archetype, a player might exhaust all of the options they built with a large hand and fall victim to a well-timed "Gorz the Emissary of Darkness".