Atlantean

"Atlantean", known as "Sea Emperor" ( Kaiō) in Japan, is an archetype of WATER Sea Serpent-Type monsters. They were first introduced in Phantom Darkness, with "Atlantean Pikeman". They later gained more members in Return of the Duelist and Structure Deck: Realm of the Sea Emperor, which also introduced their first support card, "Atlantean Marksman".

Playing Style
The focus of this archetype is to swarm the field with Level 3 or lower WATER monsters with the effects of "Atlantean Marksman", "Deep Sea Diva" and "Atlantean Heavy Infantry" 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", preferably the "Ice Barrier" Synchro Monsters.

Also, the effects of "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.

Interestingly, the 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". Here is a list of WATER Xyz Monsters that can Trigger the Atlantean's effects (note that all current Atlantean that share this effect are Level 2, 3 or 4. However, you can use cards like Lemuria, the Forgotten City for Xyz summoning some of these higher Rank monsters):

The Spell Card of this archetype, "Call of the Atlanteans", allows you to summon up to 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 later 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 destroy any card your opponent controls by sending either "Atlantean Marksman" or "Atlantean Heavy Infantry" from you Deck to the Graveyard, 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.

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 Atlantean's 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.

One of the great support cards for this Deck, "Deep Sea Diva", can Special Summon any low-Level "Atlantean" monster from your Deck. If you choose to summon Atlantean Marksman, every time you inflict battle damage to your opponent, you can Special Summon another "Atlantean" monster from your deck, like "Atlantean Attack Squad" for a beatstick, while also having monsters for a Rank 3 Xyz monsters, or Synchro material for Level 4 Synchro Monsters or above. Also you can special summon "Atlantean Heavy Infantry" with her effect which will allow you to normal summon an extra sea-serpent type monster like "Atlantean Marksman," "Atlantean Dragoons," or best of all another "Deep Sea Diva."

There are many choices for Synchro Monsters. You can go for "Ally of Justice Catastor" (Diva + Marksman or Assaultman), "Gungnir, Dragon of the Ice Barrier" (Diva + Armed Soldier + Marksman) and any other of your choice. The "Ice Barrier" Dragons discard cards to activate their effects, which clean the field by themselves. Brionac can return any card on the field to the hand any number of times in your turn, so you can use its effect to return one Atlantean monster in your field, then discard it to return another one to the hand, and since it was discarded, its effect activates.

Use "Atlantean" monsters in combination with "Koa'ki Meiru Ice". "Koa'ki Meiru Ice" will be a 1900 beater that allows you to destroy, multiple times during the same turn, a Special Summoned monster and a Set or face-up card depending on what "Atlantean" you pay for the cost with. To keep your "Koa'ki Meiru Ice" alive, you will need to have a "Iron Core of Koa'ki Meiru" or a Continuous Spell Card in your hand. A recommended Continuous Spell Card could be "D.D. Trench" or "Water Hazard".

Monsters

 * Poseidra, the Atlantean Dragon
 * Atlantean Dragoons
 * Atlantean Attack Squad
 * Atlantean Heavy Infantry
 * Atlantean Marksman
 * Abyss Soldier
 * Deep Sea Diva
 * Genex Undine
 * Genex Controller
 * Genex Ally Birdman
 * Koa'ki Meiru Ice
 * Moulinglacia the Elemental Lord
 * The Dragon Dwelling in the Deep
 * Lost Blue Breaker
 * Spined Gillman
 * Swap Frog
 * Treeborn Frog (As a Tribute for "Poseidra")
 * Mechanical Sea Dragon - Plesion
 * Mermail Abyssmegalo
 * Mermail - Abysspike
 * Skreech

Spells

 * Call of the Atlanteans
 * Salvage
 * Surface
 * Moray of Greed
 * A Legendary Ocean

Traps

 * Aegis of the Ocean Dragon Lord
 * Bubble Bringer
 * Call of the Haunted
 * Fiendish Chain
 * Safe Zone
 * Aquamirror Cycle
 * Spiritual Water Art - Aoi
 * Dimensional Prison

Extra Deck

 * Snowdust Giant
 * Bahamut Shark
 * Number 17: Leviathan Dragon
 * Evigishki Merrowgeist
 * Scrap Dragon
 * Number 20: Giga-Brilliant
 * Daigusto Phoenix
 * Gachi Gachi Gantetsu
 * Dewloren, Tiger King of the Ice Barrier
 * Gungnir, Dragon of the Ice Barrier
 * Armory Arm
 * Hydro Genex
 * Sea Dragon Lord Gishilnodon
 * T.G. Hyper Librarian
 * Mist Wurm
 * Stardust Dragon