This is the 21st Main Box and was released on July 11th, 2019. Cybernetic Rebelion introduces the Crystron archtype and adds support for Cyber Dragon, Alien, and Mermail decks.
Cyber Dragon / Cyber Twin Dragon - Easily the big fanfare of the box. Cyber Style control decks are probably the closest that will be viable with Cosmic Cyclones - can fuse into Twin and use Concentrating Current for an OTK.
Aliens - I was initially very hyped for the revealed Alien support but it seems like the prevalance of targetting is gonna make it a little weaker than advertsed. Alien Dog + Alien Ammonite and Cosmic Fortress Gol'gar are definitely better than decent for the archetype.
Mermails - Probably the big draw of the box, this seems like a mixed bag; one of the biggest criticisms of the earlier Mermails was no strong turn 1 play, but with Abyss-sphere it looks like that might change. Mermail Abyssteus is also probably the most bang for your buck, only costing 1 monster discard to SS, and replenishes the hand immediately. Mermail Abysslinde is basically Secret Six Samurai - Fuma for the archetype, and we already know how powerful he can be, so I imagine this deck will play with power level comparable to Six Samurai, but might have consistency issues. Most likely a strong Tier 2 deck.
Crystrons - I view this as a good synchro archetype too late. The lack of good generic machine synchros (as many of the current ones require Mecha Phantom Beasts), make them a lot harder to pilot. I think that this might end up being the new synchron deck of choice tho, and perhaps someone will find a way to bring them to the tier list.
Deep Sea Diva - Just favorite her if you like WATER decks, cause she's basically a 1 card lvl 3/4/5 synchro on summon. Definitely a solid card overall, and has seen plenty of action in the TCG, even being limited at one point, if I recall.
Crystrons- So I'm more excited for crystrons than alot of people seem to be. Being able to synchro summon as a quick effect can get around a weakness of synchros in general, which is being stopped by Paleozoic Canadia, Floodgate Trap Hole, Treacherous Trap Hole, Enemy Controller. Crystron Ametrix can stop you being OTK'd in combination with Crystron Citree. The Level 9 is difficult to get out but in this meta is worth it due to its effect. I think the biggest limiter is the machine synchro support we have is limited, and Citree plays will probably be the most popular combo. I can see this being tiered, but not too overpowered.
Cyber Dragon: The benefit Cyber Dragon has over Toon Cyber Dragon is attacking the turn its summoned, and being able to be used for the fusion summon of Twin Dragon. Cyber Twin Dragon is quite a weak fusion monster to be released this late into the games development, and isnt worth it. People didnt end up playing it in synchro decks either, so this support isnt very impactful.
Mermails: With the addition of Deep Sea Diva, Mermail Abysslinde, Mermail Abyssteus and Gungnir, Dragon of the Ice Barrier, I see Mermails being the most viable archtype to come out of the new box. Some combos could include Discard for Abyssteus, add Abyssdine to hand and summon it, then special summon the discarded card in the graveyard. sadly there arent any Mermail tuners, but i think Gugnir is still worth considering due to its effect. This support is in my opinion more obviously strong, especially Deep Sea Diva.
Aliens: The support for aliens in this box is Alien Ammonite, Cosmic Fortress Gol'gar and Alien Dog. Starting with Ammonite and Gol'Gar, Ammonite serves its purpose, you will quite often have a Level 4 Alien in your grave, either through battle, Neos Fusion, "A" Cell Recombination Device etc., letting you synchro into Gol'Gar. Gol'Gar's first effect doesnt seem that relevant. More often than not backrow cards will be facedown, so the a counter generation isnt reliable, just a small bonus. The second effect is better, as you are likely to have a counters on the field for a once per turn destruction. I feel like despite destruction being good, it being a once per turn effect makes it too slow to be used in this meta, either because there will be too many threats, things with destruction protection, things that want to get destroyed. Good in a vacuum, not very good in the meta. Alien Dog, not too much to say, lets you get extra A Counter generation, and board presence, not enough to make Aliens great again.
Penguins: A weak archtype whose goal is to summon/special summon Penguins to the board so they can get destroyed by your opponents monsters. Nightmare Penguin best penguin.
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