“Nephthys” is an archetype that was originally introduced in the Mini BOX Dawn of Destiny back in July 2017. If we exclude the addition of Dark Nephthys in Primal Burst, this is the first time this archetype is receiving any support, but it's also worth noting that none of these new cards even existed prior to August 2018.
The “Nephthys” archetype, similarly to “Fire King”, primarily focuses on destroying its controller's cards in order to trigger various effects.
This is a pretty standard Ritual deck that revolves around Cerulean Sacred Phoenix of Nephthys and the original Sacred Phoenix of Nephthys, but there are quite a few ways to take advantage of some of these cards.
By destroying a card in your hand, Disciple of Nephthys allows you to add another “Nephthys” monster from your Deck to your hand. Disciple of Nephthys can search Cerulean Sacred Phoenix of Nephthys, Devotee of Nephthys and Sacred Phoenix of Nephthys, so it's actually a superior option compared to Senju of the Thousand Hands.
If you destroy Sacred Phoenix of Nephthys to activate Disciple's effect, it will Special Summon itself from the Graveyard during your next Standby Phase, wiping out all Spell and Trap Cards on the field, whereas, if you destroy another copy of Disciple of Nephthys, it will allow you to add Rebirth of Nephthys or Awakening of Nephthys from your Deck to your hand during your next Standby Phase.
You can run both Senju of the Thousand Hands and Disciple of Nephthys, but this deck doesn't really need another way of searching Ritual Monsters. Card of the Soul is another great option that doesn't even take your Normal Summon.
Devotee is a Level 2 Ritual Monster, so it's quite easy to Summon with Rebirth of Nephthys. Upon being Ritual Summoned, Devotee allows you to Special Summon a “Nephthys” monster from your Deck. You can't Special Summon another Devotee or a Cerulean Sacred Phoenix of Nephthys, but you can Summon Sacred Phoenix of Nephthys or Disciple of Nephthys.
If you do Special Summon a monster from your Deck via this effect, Devotee will be destroyed during the End Phase, which will allow you to activate its second time effect on your next turn.
You can Special Summon Devotee from your Graveyard by destroying a “Nephthys” card in your hand. Use this effect to trigger Sacred Phoenix of Nephthys or Disciple of Nephthys's effect.
Cerulean Sacred Phoenix is a 3000 ATK Level 8 monster that you can Summon using the original Sacred Phoenix of Nephthys or, even better, another Cerulean Sacred Phoenix. If you Tribute Cerulean Sacred Phoenix or Devotee of Nephthys with Rebirth of Nephthys, the Ritual Spell will allow you to destroy a card on the field. You can use Chronicler of Nephthys to then get Cerulean Sacred Phoenix and Devotee back to your hand.
Once per turn, Cerulean Sacred Phoenix allows you to destroy any number of “Nephthys” cards in your hand and/or face-up on your side of the field to destroy an equal amount of monsters your opponent controls. You can destroy a face-up Awakening of Nephthys to Special Summon a Sacred Phoenix of Nephthys or one of your Ritual Monsters if they were properly Summoned before.
If it was destroyed by battle or card effect, Cerulean Sacred Phoenix of Nephthys will Special Summon itself from the Graveyard during your next Standby Phase (if it was properly Summoned before). Cerulean Phoenix is essentially a better version of the original Sacred Phoenix: better offensive stats, a better reviving effect and an additional removal effect that has great synergy with the rest of the archetype.
Since this card can be easily searched by Disciple of Nephthys and Special Summoned from the Deck via Devotee, it would be better to run just one or two copies of it. Destroy Sacred Phoenix of Nephthys to activate Cerulean Sacred Phoenix of Nephthys’s effect every turn to continuously wipe away your opponent’s backrow while also destroying any eventual monster they have.
This Skill allows Cerulean Sacred Phoenix of Nephthys to get over Koa'ki Meiru Maximus and Ancient Gear Reactor Dragon by itself; with another Level 5 or higher monster on the field (Sacred Phoenix of Nephthys or another Cerulean Sacred Phoenix of Nephthys), your main monster will reach 3600 ATK, surpassing even Silent Magician LV8.
Use Level Augmentation to increase the Level of Disciple of Nephthys, Devotee of Nephthys or Sonic Bird by 8 and then Tribute them to Ritual Summon Cerulean Sacred Phoenix of Nephthys via Rebirth of Nephthys.
The deck can generate a few weak or unplayable hands, which is definitely not ideal in the current meta. The drawback of Restart is arguably minimal if the alternative is losing the duel in the first two turns.
Going first against Koa'ki Meiru is pretty rough and, even when going second, you might have some trouble in this matchup because of Koa'ki Meiru Wall, but, generally speaking, if you manage to survive the first few turns, Sacred Phoenix of Nephthys and Cerulean Sacred Phoenix of Nephthys’s ability to come back during the Standby Phase of each of your turns will eventually outlast Koa'ki Meiru’s durability.
Every version of Koa'ki Meiru, with the exception of the Balance one, runs little to no backrow, which will make it easier to OTK your opponent on Turn 2. Use Cerulean Sacred Phoenix of Nephthys and Rebirth of Nephthys’s removal effects to clear the field and then swing directly into your opponent’s Life Points.
Just like with Koa'ki Meiru, if you manage to survive the first few turns and set up, your opponent will eventually not be able to keep up with your deck anymore. Sacred Phoenix of Nephthys is able to get rid of Vampire Kingdom and Vampire's Domain together with the rest of your opponent’s backrow whenever it’s Special Summoned by its own effect and searching those cards again can be pretty taxing for a Vampire deck. Vampire Vamp can be an issue, but, Sacred Phoenix of Nephthys will also destroy the monster equipped to it.
Silent Spellbook is possibly the worst matchup for this deck: Silent Magician is able to negate Rebirth of Nephthys, the only card you are not able to add to your hand without utilizing your Normal Summon (Sonic Bird), and Spellbook of Fate is able to get rid of Cerulean Sacred Phoenix of Nephthys and Sacred Phoenix of Nephthys permanently.
Without a Silent Magician out, this matchup is a lot easier to manage: the only threat will be Spellbook of Fate and your opponent will have to choose if they want to banish your Disciple of Nephthys right away to prevent you from destroying a potential Sacred Phoenix and then adding Cerulean Phoenix or Devotee to your hand or wait for your one of your Ritual Monsters to come out.
Paleozoic Canadia can be incredibly helpful in this matchup and, if you manage to destroy it, Sacred Phoenix will also be valuable thanks to its ability to wipe out your opponent’s backrow during the Standby Phase, forcing the activation of Spellbook of Fate.
Buster Blader, the Dragon Destroyer Swordsman + DNA Surgery completely shuts down your deck, preventing your Sacred Phoenix of Nephthys and Cerulean Sacred Phoenix of Nephthys from activating their effects, but Rebirth of Nephthys gives you an out to it with its removal effect. Paleozoic Canadia can also be used to flip Buster Blader, the Dragon Destroyer Swordsman face-down, letting Sacred Phoenix get rid of the Continuous Trap.
The Beatdown version of Nephthys Ritual really doesn’t mind having to face this deck: even if Sacred Phoenix of Nephthys ends up triggering the effect of Geartown and/or Ancient Gear Fortress when it Special Summons itself from the Graveyard, getting rid of these 3000 ATK monsters is usually not that difficult.
Masked HERO Anki is not able to get over Cerulean Phoenix naturally, so your opponent will have to use Paleozoic Canadia or Floodgate Trap Hole to put it into Defense Position. Sacred Phoenix of Nephthys’s ability to destroy all Spell and Trap Cards on the field will put a lot of pressure on your opponent’s backrow, forcing the activation of Mask Change early, and Cerulean Phoenix will then just be able to destroy it via its effect.