D/D/D+Explanation UPDATED!!!

I'm back again, edited some things and now we're at 1774 words from 1180! Also felt the need to mention this is for TCG, but could probably work in OCG too. More details on ocg at the very bottom of this giant block of text. 

EXTREMELY IMPORTANT NOTE: When a card specifies a D/D card, that INCLUDES D/D/D cards. Even the new D/D/D/D card

So before i said the boss monster was High Genghis, but thats just wrong. Your end board starting from your one card combo should be D/D/D Deviser King Deus Machinex with one material, D/D/D Wave High King Caesar, and whatever else you might have on board. Whats crazier is that you can probably do even more with more cards in hand.

Here's what they do. 

D/D/D Deviser King Deus Machinex targeted niche removal, instead of sending to the graveyard it steals the activated card. Only works on monsters, but says once per chain, meaning you can activate it as many times as you want, provided you have contracts and material to send. It doesn't negate the effects though. 

D/D/D Wave High King Caesar Negates special summon of monsters, and isn't once per turn. Meaning you can negate two Branded Fusions in a row!

Here's your combo, assuming your opponent has no negates and you start with D/D Savant Kepler and Dark Contract with the Swamp King in hand: 

Normal summon D/D Savant Kepler, effect ->Contract Gate -> D/D Gryphon, special summon it normally -> D/D/D Abyss King Gilgamesh. Set scale with Go! - D/D/D Divine Zero King Rage and D/D/D Oblivion King Abyss Ragnarok OR D/D Cerberus if you don't have a level 4 in hand. -> pend summon kepler and gryphon. If you dont have a level 4, activate cerberus to make kepler level 4. -> D/D/D Wave King Caesar -> D/D/D Marksman King Tell, activate effect to burn your opponent. Doesn't matter what you target for atk reduction. -> D/D/D Abyss King Gilgamesh using both the Gilgamesh from before and the Tell you just made. -> activate tell effect to send necro slime to grave -> activate necro slime to make D/D/D Flame King Genghis using anything but your extra deck monsters -> activate contract with swamp king, make a second lvl 6 Flame king -> xyz into D/D/D Wave High King Caesar. -> use gilgamesh to make D/D/D Deviser King Deus Machinex. 

And thats the main combo. Yeah it was a lot, and it gets even more complicated when you have material to work with in your hand already as well.  A better way to think of it is a path with checkmarks, like "Ok, I need to make gilgamesh to set scales" or, "I need to get Deviser on field with at least one contract". Take detours and just play around. 

Now a quick summary of other cards:

Swirl Slime/Vice Typhon

Use Swirl as a way to get fusions on the field, or slot in a polymerization of some type. 

Swirl+Any lvl 4 or lower D/D -> Flame King or Oracle King. After that you should have more cards to work with and make other monsters. 

Swirl+Vice OR Necro Slime -> D/D/D Flame King with Vice, D/D Flame King with slime. Then afterwards you can use Vice or Necro's effect to summon another fusion. 

Vice+any D/D in Grave -> Since you'll have most likely D/D/D Flame out, I like to summon Oracle King for 2 reasons. 1, all dark contracts heal you instead. 2, its a level 8 fusion, so if you need to you could possibly bring out Duo Dawn King. BUT, only use this if you're completely done and have no other options, because of it's effect.

Necro+any D/D in grave -> Most of the time you'd have a Flame King out. Use these to get Oracle or one of the Fusions you can. 

Other Extra Deck Monsters

Now finally, the two big Fusions. D/D/D Wave Oblivion King Caesar Ragnarok is a really good going second/mid game use, but chances are you might not get there. 

D/D/D Abyss King Gilgamesh is a good way to bring some monsters on the field, even if they're from pendulum. Every pendelum effect is literally so good in most situations, so the only bad one to pick is maybe D/D Savant Thomas. Every other one is situational, so get comfortable with their effects and when to use them. 

Now we got our synchros, D/D/D Cursed King Siegfried and D/D/D Gust High King Alexander. Siegfried a really good spell negate for your opponent's spells and on your own contracts if you don't want to take some damage. Combos include; Lamia+Vice and Orthos+Any lvl4 D/D. I personally use Gust as a big beater, since Ragnarok and Rage in your pend zones count as on the field. Usually I make him with either D/D/D Flame High King Genghis+lamia+kepler to get kepler off the field, or game 2 using High Genghis and a reborn D/D Ghost. 

D/D/D Duo-Dawn King Kali Yuga is really just a way to get a non-targeting negate on boss monsters your opponent has. An example could be you're looking at a Swordsoul Supreme Sovereign - Chengying with 20 cards in banish zone. Make a Kali Yuga and you can just beat over it. The xyz effect is also good when dealing with floodgate decks, as it's essentially a slower spell speed quick effect. 

Other Cards

Now some specific card effects I didn't mention 

D/D Gryphon allows for much more flexibility for xyz and synchro summons with it's effect. 

D/D/D Oblivion King Abyss Ragnarok is part of the main combo, you don't want to draw him so you can place him into pend zone using Gilgamesh. 

Go! - D/D/D Divine Zero King Rage same as Rag, but can also close out games if your opponent is at less than 4000 lifepoints. 

D/D Cerberus mainly used for pend effect and good scale, but in longer games his monster effect can really be clutch.

D/D Lamia easy tuner to get on field. 

D/D Orthros another tuner, easy level 4. can be used for either synchro or xyz plays.

D/D Ghost Does have a niche use, but since its not great all the time just side it. Can be used to bring materials from banish.

D/D Savant Copernicus useful to send typon or necro slime to grave (which can be used w/ vice and necro slime), and for summoning it to be a level 4 for xyz, while also being able to send necro slime or vice typhon to grave to use them for fusing. 

D/D/D Oracle King d'Arc is really funny when playing against burn decks and specifically Masquerade the Blazing Dragon. I'd side in after game 1 just in case for those decks, since it has an easy summon requirement. 

Ash and Effect Veiler are just handtraps lol, replace depending on the meta. Also the EXTREMELY rare case of making the synchros, since the D/D/D Gust High King Alexander has generic requirements and Siegfried only needs D/D non-tuners. Oh and also Barrone if you have it. 

Spell/Traps

Dark Contract with Patent License can almost act as a Dimensional Barrier. Game 1 sometimes its worth it to almost make a fusion, xyz, synchro and link monster and leave them to stop every deck (except rituals and exactly Floowandereeze)

Piri Reis Map is just a way to get Kepler for your normal. Use Small World if you're afraid of the lifepoint cost.

D/D/D Headhunt is a good way to break your opponent's board, and is searchable off of Gryphon's reborn effect.

Final Notes/Suggestions

Dark Contract with the Witch is a good board breaker. More of a card to use when you're already winning.

One for One is a niche use for kepler, but you can probably replace it. 

D/D/D Marksman King Tell's xyz effect ONLY WORKS if you've already been damaged. You can activate this turn one when using gilgamesh effect to set scales, since that makes you take damage. His grave effect is also not once per turn, letting you use the effect theoretically 4 times, as long as you find a way to put gil back in the extra deck. 

Most D/D/D extra deck monsters have this funny little effect that lets you bring back other D/D/D cards from grave. Most prominentely being Marksman Tell for his sending effect. 

Tl;dr- there is literally so much synergy here that is already here and that you can add onto it with other archetypes as well, especially fiends

I think that should be it! Leave a comment if I missed anything, or suggest something too. Anything counts, and lets try and make this have as much info as possible lmao. Ty if you made it this far, and if you didn't hopefully you'll find the actual deck as a good inspiration/reference tool.

Update: After a few months I edited it a bit more. Some flex cards you can put in are as follows-

Baronne de Fleur instead of D/D/D Gust High King Alexander 

Small World instead of Piri Reis Map if you don't like halving your lifepoints

You could replace 1 D/D/D Vice King Requiem with a Dark Contract with the Swamp King if you feel you don't draw it enough

Divine Arsenal AA-ZEUS - Sky Thunder is another thing you could add, specifically for xyz climbing. 

Any relevant handtraps instead of Ash or Veiler, like Nibiru, the Primal Being or Droll & Lock Bird, even Kaijus. Anything but Dimension Shifter 

For OCG you could probably put in Predaplant Verte Anaconda and some wack ass dark fusions, but I'm not about to brew a crazy ocg d/d/d fusion thing. At least not for another 6 months. 

In conclusion, D/D/D's are literally that one rogue deck that got everything it needs and still isn't meta. Honestly I like it that way, it means the cards are cheap lol. I swear if D/D gets more support I'll be back with over 2k words. Good luck out there