"Atlantean", known as "Sea Emperor" (
The focus of this archetype is to swarm the field with Level 3 or lower WATER monsters with the rank-and-file's regular effects to later Tribute them for the summon of their ace monster, "Poseidra, the Atlantean Dragon", or to Synchro Summon with "Deep Sea Diva" and "Genex Controller".
The effects of many "Atlanteans", such as "Atlantean Marksman", "Atlantean Heavy Infantry" and "Atlantean Dragoons" trigger when they are sent to the Graveyard as cost for a WATER monster's effect, so cards like "Abyss Soldier" and "Gungnir, Dragon of the Ice Barrier" would be a good add to the Deck.
"Atlantean" effects also activate if they are detached from an Xyz Monster (the effect only requires the monster to be sent to the Graveyard, like "Dandylion"), so a great addition to this deck are WATER Xyz Monsters, like "Number 17: Leviathan Dragon". While most "Atlanteans" are Levels 2, 3, and 4, "Lemuria, the Forgotten City" can help with Xyz Summoning and Synchro Summoning.
The primary Spell Card of this archetype, "Call of the Atlanteans", allows you to Summon 3 Level 3 or lower Sea Serpent-Type monsters from your Graveyard, but you can't Special Summon the turn it is activated, and there must be at least 3 acceptable monsters in your Graveyard. Since most of the effects of "Atlantean" activate when they are sent to the Graveyard, the latter shouldn't be so hard, but cards like "Skreech" can help you dump cards. "Call of the Atlanteans" is a Quick-Play Spell Card, you can activate it during your opponent's End Phase, so you can Special Summon normally in your turn, as long as it was set before.
"Atlantean" Decks run cards that clean the field before attacking. "Genex Undine" can activate a plethora of "Atlantean" effects, while adding a "Genex Controller" (a Level 3 Tuner) to your hand. "Abyss Soldier" and "Abyss Warrior" can trigger the effect of the "Atlantean" monsters while returning a monster to the hand and a card in the Graveyard to the top or bottom of the Deck, respectively. Another great card is "Deep Sea Diva", as she can fetch almost all of the low-Level "Atlanteans" and provide them with Synchro or Xyz material.
This archetype also goes hand-in-hand with the "Mermail" archetype since most of the "Mermails'" effects involve discarding a water monster as a cost which will in turn activate the "Atlanteans'" effects. By using "Mermail Abysspike," "Mermail Abyssturge", and/or "Mermail Abyssmegalo" with the "Atlanteans" you will be able to activate their useful effects and the "Atlanteans'" effects together.