Introduced in Abyss Rising, the Mermails are basically Merfolk(Mer) outfitted with Armor(Mail), which is where the name of their Archetype comes from.
There are 3 types of Mermail Monsters, Mermonsters (Level 7 Sea Serpents), Mermen(Level 4 Fish) and Mermaids(Level 3 Aqua).
Most of the Mermails have effects that can only be activated once per turn, so watch out for that.
In this guide, I will only explain the playable Mermails, ignoring the other non-playable ones.
Water/Sea Serpent – Effect/7/2400/1900
During your Main Phase: You can discard 2 WATER monsters, except this card; Special Summon this card from your hand. When this card is Special Summoned by this effect: Add 1 “Abyss” Spell or Trap Card from your Deck to your hand. You can Tribute 1 other face-up Attack Position WATER monster you control; this turn, this card can attack twice during the Battle Phase.
The main boss monster of the Mermails and is currently the only Mermonster Pre-CBLZ. Its Summoning Condition is actually an Ignition Effect, so discarding the 2 other Water monsters to the Graveyard is a Cost, that allows the Atlanteans to trigger their Effects when discarded for Megalo.
Its Summoning Condition being an Ignition Effect has other advantages too, because its Summon cannot be negated by cards like Solemn Judgment or Thunder King Rai-Oh.
The disadvantages are that your Opponent can Chain Maxx ”C”, Debunk or Mind Crush to its Effect.
When it is Summoned by its 1st Effect, you can search for one Abyss Spell/Trap card from your deck to your hand. Your main target for this Effect would be Abyssphere, the other Abyss Spell/Traps are not really that good.
The 3rd Effect is very important, allowing you to take out big chunks out of your opponent’s Life Points. It has an OTK with Deep Sea Diva which I will explain in the Combos Section of the Guide.
Note that it says Tribute 1 other face-up Attack Position WATER monster you control, most players miss out the Attack Position part of the Effect and tribute their Defence Position Water Monsters for the Effect by mistake.
Water/Fish – Effect/4/1600/800
When this card is Normal or Special Summoned: You can discard 1 WATER monster; add 1 Level 3 WATER monster from your Deck to your hand. The effect of “Mermail – Abysspike” can only be activated once per turn.
Your most common target to summon with Linde’s Effect. Works like a free MST when used with Marksman.
Its range of targets are Atlantean Marksman, Genex Undine and Mermail Abysslinde.
Its Effect specifically states Level 3 Water Monsters, not Level 3 or lower, so remember not to search out other cards like Diva and Heavy Infantry.
Water/Aqua/3 – Effect/1500/1200
If this card on the field is destroyed and sent to the Graveyard: You can Special Summon 1 “Mermail” monster from your Deck, except “Mermail – Abysslinde”. The effect of “Mermail – Abysslinde” can only be activated once per turn.
The floater of the deck, brings out another Mermail monster from your deck other than itself when it is destroyed and sent to the Graveyard.
Doesn’t have a Level Limit, so it can even bring out Megalo.
Main target for Abyss-Sphere since the drawbacks of Sphere don’t affect this card and can trigger its Linde’s Effect when it is destroyed.
Its attack of 1500 is just high enough for Bottomless Trap Hole to hit it, so watch out for that as you don’t get Linde’s Effect when it is Banished.
Continuous Trap Card
Special Summon 1 “Mermail” monster from your Deck, but its effect(s) is negated. While this card is face-up on the field, you cannot activate Spell Cards. When this card leaves the field, destroy that monster. Destroy this card during your opponent’s next End Phase after activation.
This is the card that makes Mermails such a fearful deck to play against. If your opponent plays a blind MST and targets this card, you can just chain it to bring out Linde, Linde gets destroyed and you can Summon another Mermail from your deck, your opponent just -1ed himself.
You can even bring out Linde to block an Attack while triggering Linde’s Effect.
Mind its drawback that prevents you from activating Spells while it is face-up on the field, most players tend to miss that out.