Atlantean Deep Sea Icejade (Theme Chronicle 2024)

Icejade is one of my favorite archetypes ever, and I generally like WATER strategies whenever they're playable. And surprisingly... in Theme Chronicle this is an entirely playable strategy! Not the best thing you could be playing, but one that can grind it out with the best and get you the wins for those sweet, sweet gems.

This decklist is an altered version of one I actually encountered in the event, so I cannot take credit for making this. I will, however, explain the deck to the best of my ability to hopefully make it easier to learn. It's not an especially difficult deck, but information can help you understand how to build your own version and thus be able to improve upon it should you choose to do so.

The deck is comprised of about two engines made up of three archetypes, the Atlantean+Deep Sea providing Synchro plays and material, while the Icejade cards provide further material and a control tool in Icejade Erosion. It's relatively consistent to get into something across the deck, as both engines net you at least one disruption if you don't get interrupted and decent follow-up for next turn.

Icejade

• 2x Icejade Aegirine searches any Icejade Spell/Trap on summon, and then revives a WATER if your opponent targets her in any way. The exact target for her search depends on the game state, though I usually favor Erosion if I opened Aegirine with no other relevant cards in hand.
• 2x Icejade Tremora allows us effectively free Special Summons of WATER monsters from our hand, just generically useful. If an Icejade is destroyed (including by your own cards) while Tremora's in the GY, she can also banish herself to summon an Icejade from hand or GY.
• 2x Icejade Ran Aegirine is an excellent last support card for Icejade, as is still extremely good here. Discarding a WATER (which triggers the Atlanteans, more on that later) allows you to summon her plus an Icejade token. This token locks you into WATER while its on the field, but the material allows you to make a WATER Level 10 Synchro (though they're banned in this event, so no Aegirine Gymir or Chengying for us here) or a WATER Link-2 (Abyssalacia or Coral Anemone, probably). 
• 1x Icejade Creation Kingfisher is a method of removal and a bit of extra extension if we need it. Entirely removable if you so desire, but being able to bounce an opponent's card back to hand is useful enough that I keep it around.
• 2x Icejade Cradle searches any Icejade monster. Not a once per turn, either.
• 1x Icejade Manifestation allows you either Foolish Burial or Emergency Teleport an Icejade if you control a WATER and your opponent has a monster on field or in grave.
• 1x Icejade Erosion is a once per turn repeatable negate of any card on the field for the cost of destroying an Icejade monster you control. And if your opponent gets clever and tries to banish your WATER monsters from field (or shuffles them into hand/deck), Erosion lets you summon an Icejade straight from your deck.

Atlantean+Deep Sea

• 2x Neptabyss, the Atlantean Prince is a potent card, though not quite a one card starter. He can send an Atlantean from deck to grave as cost (which triggers the effects of Infantry and Dragoon) to search an Atlantean of choice. Usually you send Dragoons to search Heavy Infantry, but occasionally sending Infantry to destroy something can be useful depending on board state. 
• 1x Atlantean Heavy Infantry grants you a second normal summon for Sea Serpent monsters, and if sent to the GY to activate a WATER monster effect (IE, sent as cost) it destroys a face-up card your opponent controls.
• 3x Deep Sea Diva is a classic Tuner, and still a potent one. By Normal Summoning her (not Special Summon), you can summon any level 3 or lower Sea Serpent straight from your deck. 
• 2x Deep Sea Minstrel is one of our targets for Diva, and more importantly a tool to get rid of handtraps so you can play uncontested. You can discard Minstrel and another WATER (as cost, so Atlanteans are triggered by this, so Dragoons+Minstrel is a very fun opening hand) to look at your opponent's hand and banish one card from it until the end phase.
• 1x Guitar Gurnards Duonigis is the other target for Diva. It can double the level of one Level 4 or lower WATER for the turn, allowing access higher level Synchros off just Diva. It also banishes cards from your opponent's deck equal to the number of WATER monsters you control when it was Special Summoned, which is important for Deep Sea Repiteur since it needs your opponent to have banished cards.
• 3x Atlantean Dragoons. Send this as cost (for another monster) to search a Sea Serpent, and that's basically it. The on-field effect is not relevant ever, since the Sea Serpents we run have very low attack in the first place.
• 2x Deep Sea Aria to search Diva (or another Sea Serpent, but usually Diva), if you can get another WATER into the grave (which is not especially difficult).

Non-Engine

• 3x Ash Blossom, 3x Maxx 'C', 2x Called By the Grave, 1x Crossout Designator, 2x Infinite Impermanence. Handtraps and anti-handtraps, these are generically useful and all legal in this event. I'd be running these in any deck I'd run for this deck.
• 1x One for One to summon Neptabyss for the cost of a discard. Note that it cannot activate the effects of the Atlanteans, since One for One is not a WATER monster.
• 3x Synchro Overtake. By revealing Deep Sea Repiteur, you can either add Diva to your hand or Special Summon her. Diva's effect only activates when she is Normal Summoned, so you may just want to add her to your hand and normal her.
• 1x Moulinglacia the Elemental Lord. If you have exactly 5 WATER monsters in your grave, you can SS it from your hand, and then forcibly discard two random cards from your opponent's hand. The only weakness is that if it is removed from the field, you skip the Battle Phase of your next turn. This can be prove annoying, but the card itself is potent enough to be worth the downside.

Extra Deck (only one copy of each card, I generally haven't found too much need for extra copies of anything)

• Tatsunoko allows one to Synchro Summon using cards in your hand as material, allowing you to turn an otherwise off-line Icejade Tremora into a Level 8 Synchro (or any other combination to make a Synchro with a Level 3 Tuner, use your imagination). You can make this with Deep Sea Diva+Neptabyss.
• Herald of the Arc Light is an omni-negate+minor floodgate, made using Diva+Infantry if you so desire. The GY effect does not have any use in this deck, as we don't play any Rituals.
• Deep Sea Repiteur is required for Synchro Overtake to function, and is fairly functional regardless. While her on-field effect is mostly irrelevant even in this lower powered format, her effect when sent to the GY is just a straight Monster Reborn for Level 5+ WATER monsters, though you're locked into WATER for the rest of the turn afterward.
• Coral Dragon, a classic bit of removal for Synchro decks and one easily made with Diva+Dragoons. Discard (which does count for the Atlantean cards' effect when discarded) to destroy a card on field. And if it gets sent to the GY, you even get a draw.
• Deep Sea Prima Donna is a surprisingly strong card, one that is basically limited by the rest of WATER decks not being strong enough to really leverage its power. Put a banished card back into your opponent's hand to summon any Level 4 or below WATER monster from your deck (or add it your hand). Make this using Diva+Guitar (by using Guitar's effect on Diva). When she's sent to the GY, she'll even shuffle any banished card back to the deck (including whatever you banished with Minstrel's effect, if you so desire). 
• White Aura Whale is one of our two main bosses (at least, ones you'll realistically summon), and is our offensive tool for getting inton a game winning state. On summon it's basically Lightning Storm's anti-monster effect, and it can attack twice on monsters while inflicting piercing battle damage. If it ends up destroyed, you can banish another WATER from your GY to revive it as a Tuner, which is not a once per turn.
• Adamanicpator Risen - Dragite is our other boss monster, and our defensive tool going first. If you have a WATER in grave, you can negate a Spell/Trap every turn. The other effect is useless in this deck, since we run no other Rocks. Both this card and White Aura Whale can be made by Diva+Guitar (using Guitar effect on itself to make it a 6), or with Prima Donna+Neptabyss.
• I:P Masquerena is a generic Link-2 you can go into if you have to for whatever reason. I haven't had it as part of an end-board yet, nor do I find opportunities where I wouldn't rather make something else, but it works and we do not have a lot of good alternatives.
• Mistar Boy is just WATER support to help boost our damage. It's generally a struggle to OTK, so we'll take as much help as we can get. Also grabs a WATER and adds to hand when destroyed by your opponent, which is helpful.
• Mermail Abysslacia is a back-up plan, and a generically solid Link-2 for the deck. Her effect to search a Mermail is not applicable to this deck, as we do not have main-deck Mermails (none fit especially well, though Abyssdine, Abyssteua, and/or Abysspike might be generically good enough to consider), but her effect when the opponent destroys her is a solid advantage generator by allowing you to both Foolish Burial a WATER (for cost) then revive a WATER of your choice. Since you rarely get OTK'd in this format (in my experience), you can use this to sit on if you can get two monsters onto the field (that are Fish/Sea Serpent/Aqua) and maybe be able to follow up next turn.
• Knightmare Phoenix is generic Spell/Trap removal that's easily made.
• Marincess Coral Anemone revives a WATER that's below 1500 ATK. Easy to make, and helps push damage in general.
• Knightmare Unicorn is easily made removal for anything that has an effect when destroyed (or can't be destroyed), since it shuffles the target back into deck.
• Knightmare Gryphon I have never made and probably won't ever make. It's a lot of investment for a psuedo-Skill Drain, and we're generally better off with other tools most of the time.
• Mekk-Knight Crusadia Avramax is in a similar boat. I just slotted him in because there's little else to put in. Avramax made with I:P probably isn't outable by most decks, though, so you can definitely get some benefit if you need to.