+ Create a Synchro Monster +

[Flash Flyer - Sakura]

Saggi the Epidemic Clown
Level 5 | DARK | Spellcaster | Synchro | Effect
1000/2500
1 DARK Tuner + 1+ non-Tuner DARK monsters
When this card is Special Summoned: You can reveal 3 "Virus" Traps from your Deck; your opponent chooses 1 for you to add to your hand, also shuffle the rest into the Deck. (Quick Effect): You can switch this card's ATK/DEF until the End Phase of this turn. You can only use each effect of "Saggi the Epidemic Clown" once per turn.

ATK/DEF are 40% higher than original Saggi (and conveniently can change his stats to match the requirements for all of them that actually matter).

Now ask whether this card can be run in Lair of Darkness (I think they run Tuners, but idk).

=====
1. "S-Acceleranimal" monster
2. Synchro that can make use of the new changes to MR4 announced recently.
3. Synchro that can plus hard off of Super Rejuvenation.
4. LIGHT Beast-Warrior Synchro

[The Nepfessor]

Warbeast Shining Vixen
Level 6 LIGHT Beast-Warrior/Synchro/Effect
2300/1800
1 Tuner + 1+ non-Tuner monsters
If you Synchro Summon this card, all materials must be the same Type. Your opponent can only activate 1 Spell/Trap Card or its effect once per turn. Banish any monster destroyed by battle with this card, face-down.

Retrain any Ritual Monster into a Synchro Monster, with an effect that punishes Special Summoning with a Spell/Trap effect.

[Flash Flyer - Sakura]

Saffira Zeta, Radiant Queen of Dragons
Level 6 | LIGHT | Dragon | Synchro | Effect
2500/2400
1 Tuner + 1+ non-Tuner LIGHT monsters
When a Spell/Trap Card, or monster effect, is activated that includes an effect that Special Summons a monster(s) (Quick Effect): You can discard 1 card; negate the activation, and if you do, destroy that card. During the End Phase, if a LIGHT monster was Summoned or sent from the hand or field to the GY: You can activate 1 of these effects.
● Shuffle 1 card from your opponent's hand into the Deck.
● Special Summon 1 LIGHT monster from your hand or GY.
You can only use each effect of "Saffira Zeta, Radiant Queen of Dragons" once per turn.

"Zeta" should be the 6th letter of the modern Greek alphabet (and should be a reference to Level); do correct me if I'm wrong. But yeah, it's Saffira retrained as a Synchro.

====
1. "S-Acceleranimal" monster
2. Synchro that can make use of the new changes to MR4 announced recently.
3. Synchro that can plus hard off of Super Rejuvenation.
4. Requires either 3 or more Tuners OR 3+ non-Tuner monsters; you have a choice.

[The Nepfessor]

Emperor of the Tundra
Level 12 WATER Aqua/Synchro/Effect
2000/2000
1 Tuner + 3+ non-Tuner monsters
Must be Synchro Summoned. Gains ATK equal to the combined Levels of the non-Tuner monsters used for its Synchro Summon x 200. If this card is destroyed by battle, and all the Synchro Materials that were used for its Synchro Summon are in your GY: You can shuffle them into the Deck, then draw 2 cards.

Also, yes, Zeta (ζ) is the 6th letter of the Greek alphabet.

N/C: A Level 10 or higher evolution for XX-Saber Gottoms.

[Flash Flyer - Sakura]

XXX-Saber Gottoms Magna
Level 12 | EARTH | Beast-Warrior | Synchro | Effect
4100/3600
1 Tuner + 1 non-Tuner EARTH Synchro Monster
This Synchro Summoned card cannot be targeted or destroyed by an opponentʻs card effects. You can Tribute 1 EARTH monster; banish 1 card from your opponentʻs hand or field. This is a Quick Effect if this card was Synchro Summoned using "XX-Saber Gottoms" as material, also your opponent cannot activate cards or effects in response to this effectʻs activation. If this card is destroyed: Special Summon 1 Level 10 or lower EARTH Synchro Monster from your GY.

=====
1. "S-Acceleranimal" monster
2. Synchro that can make use of the new changes to MR4 announced recently.
3. Level 7 or 8 Dragon (see Signer Dragon stuff)
4. FIRE Synchro

[The Nepfessor]

Bonfire Goliath
Level 7 FIRE Pyro/Synchro/Effect
2400/800
1 Tuner + 1+ non-Tuner FIRE monsters
(Quick Effect): You can banish 1 FIRE monster from your GY, then target 1 face-up monster your opponent controls; its ATK becomes equal to the DEF of the banished monster, until the end of this turn. You can only use this effect of "Bonfire Goliath" once per turn. After damage calculation, if this card attacked an opponent's monster: Gain LP equal to that monster's original ATK.

N/C: Make a Synchro Tuner that benefits itself if used for a Synchro Summon of another Tuner Synchro Monster.

[Flash Flyer - Sakura]

Comet Accelerator
Level 4 | EARTH | Rock | Synchro | Tuner | Effect
1900/1200
1 Tuner + 1+ non-Tuner monster
Once per Chain, during your opponent's Main Phase, you can (Quick Effect): Immediately after this effect resolves, Synchro Summon using this card you control. When this card is used as Synchro Material for a Tuner Synchro Monster: You can Special Summon this card from your GY, and if you do, draw 1 card.

====
1. Pendulum Monster
2. Synchro that can make use of the new changes to MR4 announced recently.
3. Level 7 or 8 Dragon (see Signer Dragon stuff)
4. Allows you to look at opponent's hand or Deck for verification.

[The Nepfessor]

Nirvana Magician
Level 8 Scale 1 DARK Spellcaster/Synchro/Pendulum/Effect
2500/2000
Once per turn: You can target 1 Pendulum Monster you control; if that target attacks this turn, you can send 1 card your opponent controls to the GY.
----
1 Tuner + 1+ non-Tuner monsters
If this card is Synchro Summoned using a "Magician" Pendulum Monster as Material: You can target 1 Spell in your GY; add it to your hand. You can only use this effect of "Nirvana Magician" once per turn. When this card destroys an opponent's monster by battle: You can gain LP equal to that monster's original ATK. If this card in the Monster Zone is destroyed by battle or card effect: You can place this card in your Pendulum Zone.

Enlightenment Paladin retrained as a Pendulum Monster, being part of the "Magician" theme.

N/C: Make a Synchro Monster that, like Majestic/Neos Fusions, they return to the Extra Deck during the End Phase (do NOT make a Majestic Synchro).

[Draconus297]

Rejuvenation Synchron
LIGHT - Level 6 - Warrior/Synchro/Tuner/Effect - 0/2500
1 "Synchron" Tuner + 1 or more non-Tuner monsters
When this card is Synchro Summoned, you can target 1 Level 6 or lower "Warrior" Synchro monster in your Graveyard: Gain LP equal to its ATK, then, if you gained less than 2500 LP this way, draw 1 card. During the End Phase: Shuffle this face-up card into your Extra Deck, then Special Summon as many "Warrior" Synchro monsters with different Levels as possible from your Graveyard. If you control another face-up Synchro monster, you can choose not to apply this effect. You can only activate each effect of "Rejuvenation Synchron" once per turn.

1. Create a monster that's a decent on-field Synchro, but also works as Quasar fodder.
2. Create a Synchro evolution to a Tuner that you find personally interesting.
3. In the anime, there was a non-Effect Insect Synchro that was Summoned alongside a card called "Tripwire", which prevented all effects that can activate on your opponent's turn from activating at all (meaning no Stardust protection for Yusei, even on his own turn). Cut out the middleman?

[The Nepfessor]

Sea Jewel Dragon
Level 6 WATER Sea Serpent/Synchro/Tuner/Effect
2600/0
"Lappis Dragon" + 1 non-Tuner monster
If this card is Synchro Summoned: You can send 1 Sea Serpent monster from your Deck to the GY, whose Level is lower than this card's on the field, and if you do, reduce this card's Level by that monster's, but for the rest of this turn, you cannot activate the effects of monsters with the same name the sent monster had in the GY. You can discard 1 card, then target 1 Sea Serpent monster in your GY, except "Sea Jewel Dragon"; add it to your hand or place it to the top of your Deck. You can only use each effect of "Sea Jewel Dragon" once per turn.

N/C: Materials are "Phonon Pulse Dragon" + 1+ non-Tuner monsters

[Flash Flyer - Sakura]

Phonon Blast Wave Dragon
Level 8 | DARK | Dragon | Synchro | Effect
2700 | 1400
"Phonon Pulse Dragon" + 1+ non-Tuner monsters
When this card is Special Summoned: You can declare a Level from 1 to 10; all other monsters you control become that Level, also you cannot Special Summon for the rest of this turn, except Synchro Monsters. Once per turn: You can target 1 non-Tuner monster you control; that monster is treated as a Tuner monster. You can only Special Summon "Phonon Blast Wave Dragon(s)" once per turn.

You can't make Xyz plays if you do this, however it does make Quasar and stuff much more manageable if you really have to. Or you can wait until next turn to Rank 10 or something.

====
1. Level 7 or 8 Dragon (see Signer Dragon stuff)
2. Allows you to look at opponent's hand or Deck.

[Draconus297]

I'll do both.

Knowledge Dragon
EARTH - Level 8 - Dragon/Synchro/Effect - 1000/2800
1 Tuner + 1 or more non-Tuner monsters
You can destroy 1 card you control, then declare 1 card type (Monster, Spell, or Trap): Excavate cards from the top of your opponent's Deck until you excavate a card of the declared Type. If you do, banish that card, then arrange all remaining excavated cards (if any) on top of your opponent's Deck in any order. If you excavate no cards of the declared Type, shuffle your opponent's Deck. You can only activate this effect of "Knowledge Dragon" once per turn. If a card(s) your opponent owns is banished: You can destroy 1 card on the field, then increase the ATK of all monsters you control by 500.

1. Create a Synchro that functions both as a solid boss and as good Quasar fodder.
2. Create an Insect Synchro that blocks Quick Effects.
3. Create a "partner" Synchro to any of the Signer/Dimension Dragons, whose effect specifically complements theirs for devastating effect.

[Flash Flyer - Sakura]

Life Stream Fairy Wyvern
Level 6 | LIGHT | Dragon | Synchro | Effect
2100/1500
1 Tuner + 1+ non-Tuner monsters
You take no effect damage. Once per turn, if a card(s) on the field are destroyed by a Dragon Synchro Monsterʻs effect: You can activate 1 of these effects;
● Shuffle up to 2 cards on the field and/or in the GYs into the Decks.
● Special Summon 1 Level 4 or lower monster from your hand or GY.

Well...this is intended to work with Ancient Fairy Dragon (but she's still banned, so you got Pixie as a backup), though this also works with Stardust / RDA and to some extent, Black Rose (if you can protect this from getting blasted too).

Also gives Ruka another in-canon boss monster to sit on until Konami unbans her Signer Dragon.

=====
1. Synchro for archetype/series that lacks one.
2. Requires 3 Tuners
3. Make a new Synchro for Jack Atlas (either 5Ds anime/manga, ARC-V or combo of either of them is fine)

[Draconus297]

Red Dragon Archfiend - Emperor
DARK - Level 12 - Dragon/Synchro/Effect - 4500/3000
2 Tuners + 1 non-Tuner "Red Dragon Archfiend" monster
Cannot be destroyed or targeted by your opponent's card effects. If your opponent Special Summons exactly 1 monster from their hand, Graveyard, or Extra Deck (Quick Effect): You can destroy all monsters your opponent controls with less ATK than this card, then, you can Special Summon 1 FIRE Fiend "Red" monster, DARK Dragon Synchro monster, or "Resonator" monster from your Graveyard whose ATK is less than or equal to the combined ATK of the destroyed monster(s). You can only activate this effect of "Red Dragon Archfiend - Emperor" once per turn. If the effect of a "Red Dragon Archfiend" Synchro monster is activated, except "Red Dragon Archfiend - Emperor": You can banish a number of cards from the field or Graveyard equal to the number of other "Red Dragon Archfiend" monsters you control.

1. Create a Synchro that is good as both Quasar fodder and a field boss.
2. Insect Synchro that blocks Quick Effects.
3. A reason to run a bunch of Normal Traps.

[Flash Flyer - Sakura]

Jamming Wave Spider
Level 7 | DARK | Insect | Synchro | Effect
1200/2400
1 Insect Tuner + 1+ non-Tuner Insect monsters
Neither player can activate the Quick Effects of monsters in their possession. Once per turn, if this card would be destroyed by battle or card effect, you can pay 1000 LP instead.

This would also be a good Roman card for 5D's legacy support.

=====
1. New Signer Dragon
2. Make Synchro for an archetype that doesn't have one, but has the resources to make it consistently enough.
3. Let's make a Cyberse Synchro that has nothing to do with Yusaku.

[Draconus297]

Digit Deletion Driver
DARK - Level 7 - Cyberse/Synchro/Effect - 1700/2800
1 Tuner + 1 or more non-Tuner monsters
Your opponent's monsters lose ATK equal to the combined Levels of all monsters you control x100. Once per turn, you can target 1 monster your opponent controls with less ATK than this card (Quick Effect): Negate the effects of all cards your opponent controls in the same column as that target, until the End Phase. If this card destroys your opponent's monster by battle, you can select and apply 1 of the following effects:
●Increase this card's Level by the Level of the destroyed monster.
●Inflict damage to your opponent equal to half the destroyed monster's original ATK.

1. It must be both good Quasar fodder and a functioning field boss.
2. Provides a reason to run a bunch of Normal Traps.
3. Must be able to treat some other subtype as Tuner (think Nirvana High Paladin).

[Flash Flyer - Sakura]

Let's do option 1, though that probably limits me to Levels 4-7 if you want to make it using 3 materials only.

Hurricane Wyvern
Level 6 | WIND | Wyrm | Synchro | Effect
2500/1600
1 Tuner + 1+ non-Tuner monsters
For this card's Synchro Summon, you can treat 1 non-Tuner WIND monster you control as a Tuner. Once per turn: You can target 1 other monster on the field with equal or less ATK than this card; shuffle it into the Deck. A Synchro Monster that used this card as material cannot be Tributed.

Now I'm going to try building a Yusei deck and beat the YGOPro AI doing stuff (well, mostly because MR5 let us go back to 5Ds spam)

====

1. Accel Synchro
2. Red Nova Dragon crossover (see T.G. Expansion for Shooting Star)
3. Can treat Links and Xyz Monsters as having equivalent Levels.

[Draconus297]

Red Nova Dragon - Archfiend's Synchron
DARK - Level 12 - Dragon/Synchro/Effect - 3500/3000
2 Tuners + 1 non-Tuner Dragon Synchro monster
Cannot be destroyed or targeted by monster effects. Gains 500 ATK and DEF for each Tuner in your Graveyard. If your opponent's monster attacks, or activates a monster effect, you can banish this card from your field until your next Standby Phase (Quick Effect): You can Special Summon 1 "Synchron" or "Resonator" Tuner from your hand or Graveyard, and if you do, you can add 1 Tuner monster from your Deck or Graveyard to your hand whose Level is exactly equal to the Level of the Summoned monster. If this card leaves the field due to the effect of a card your opponent owns: You can Special Summon up to 1 each of a "Red Dragon Archfiend" and "Warrior" Synchro monster from your Graveyard. You can only activate each effect of "Red Nova Dragon - Archfiend's Synchron" once per turn.

Jack and Yusei are frequently described as great friends, but their Decks have literally zero overlap outside of "being Synchro based". So . . . let's see someone face down RDA Scarlight and Junk Warrior as punishment for dropping a Lightning Storm, Nibiru, or even an Evenly Matched (remember, "effect of an opponent's card" means that, because Evenly was still your opponent's card, it doesn't matter that you chose to let Archfiend's Synchron die).

1. Give a reason for a Synchro Deck to be full of Normal Traps.
2. Combine effects in such a way that a LP replenishing effect is hugely important.
3. Combine the effects of two old, crappy boss monsters that no sane person runs.

[Flash Flyer - Sakura]

Let's see, no one bothers to run the original HERO Fusions, so...let's do something like that. (And no, that guy on Duelingbook everyone hates doesn't count.)

Blitz Flare Dragon
Level 7 | LIGHT | Dragon | Synchro | Effect
2500/2100
1 Tuner + 1+ non-Tuner monsters
Once per turn: You can target 1 monster on the field; destroy it. This card cannot attack the turn you activate this effect. If this card destroys an opponent's monster by battle: Inflict damage to your opponent equal to that monster's ATK or DEF (whichever is higher).

(This is basically a 5Ds era design without hard OPT; I sure hope that no one is abusing that first effect with duplicates or some dirty ass revival loop.)

====
1. Accel Synchro
2. Signer Dragon (or equivalent of one, so...Level 7 or 8). You have free reign over everything else
3. Can treat Links and Xyz Monsters as having equivalent Levels.

[The Nepfessor]

Vernage, the Otherworldly Blessing
Level 6 FIRE Reptile/Synchro/Effect
2500/2800
1 Tuner + 1+ non-Tuner monsters
If this card is Synchro Summoned: It gains ATK equal to the number of Normal Traps in your GY x 300. (Quick Effect): You can target 1 Normal Trap in your GY; apply that target's effect, then shuffle that target into the Deck. You can only use each effect of "Vernage, the Otherworldly Blessing" once per turn.

N/C: Make an evolution for "Junk Warrior"

EDIT: Was ninja'd by Sakura, so...

Scrapyard Paladin
Level 7 EARTH Warrior/Synchro/Effect
2600/2400
1 Tuner + 1+ non-Tuner EARTH monsters
For this card's Synchro Summon, you can treat 1 face-up Trap you control that is a monster as a Tuner. When a Trap Card or effect is activated (Quick Effect): You can target 1 Continuous Trap in your GY; Set it to your field, also it can be activated this turn. You can only use this effect of "Scrapyard Paladin" once per turn.