There's a lot of buzz around the Apophis (Odion) cards, especially around possible supplemental engines to help you combo and break boards. I've heard most people talk about the Kashtira engine as the best option for a true one-card combo by going into Arsenal Falcon, making Romulus, and dumping Destrudo with Zephyros in rotation to make AFD and get into the new field spell. I think this avenue fails for a number of reasons, but most importantly:
1. It uses your normal summon anyway for Kashtira Riseheart, so you are unable to use Man with the Mark as a starter if you go for the Fenrir 1-card combo.
2. If you get interrupted on your Arsenal Falcon, or your Romulus, or even your Fenrir, you're SOL. If you don't have Called By/Crossout and they negate your Falcon, you have no follow-up beyond hard drawing Treasures of the Kings--which, if you did that, why are we bothering with the convoluted Kashtira combo anyway?
Obviously using Fenrir as a starter allows you to have a true 1-card combo--the material you start with gives you a line into Silhouhatte Rabbit without needing anything else in hand other than a discard to Ravine, but the inherent fragility and non-extensibility of this line makes me shy away from it.
However, by using a small Dragon Ravine package as a supplemental engine, we can achieve largely the same effect while also providing some much needed flexibility and resiliency to the main combo. Man with the Mark remains our primary starter, with Anubis and Small World as a way to search out. Iff they negate the Man with the Mark, and you have any of the five ways to get to Dragon Ravine (3x Remus, 2x Ravine), you can use Ravine to dump Destrudo and go into AFD using the Man with the Mark. This gameplan DOES still require you to have an extra card to set to trigger the Treasures of the Kings, but that can be solved with some clever deckbuilding to make sure you have enough settable cards to fulfill this requirement while maintaining a good core engine and non-engine base.
In addition, having so much access to Dragon Ravine means, even without Man with the Mark, starting with Ravine and any non-Tuner normal summon means you can go into AFD and Apophis combo WITHOUT using Man with the Mark. This line is obviously more fragile--but it also means more hands are playable, even with a solid number of hand traps. Because of this, we need our hand traps to be non-Tuners--which means no ghost girls or Effect Veiler. We also need our hand traps to be ultra-impactful. This deck has a hard time going second, so we need our non-engine to be solid board breakers or game-ending hand traps. For that reason, we're playing Fuwalos, Droll, and Nibiru. In order to maintain a high number of Spells/Traps to set alongside our Treasures of the Kings, we're playing Impermanence and Book of Eclipse, as we need these to be useful going second but also fine to set on our own.
The Book of Eclipse slot could also be used for Forbidden Droplet instead. However, I default to Book for a few reasons:
1. We're already so card hungry with Dragon Ravine as an extender and Small World as a searcher, that it can be difficult to even have enough material for Droplet to good work into an established board.
2. Book of Eclipse can actually be used as an insulator against targeted negation when attempting to resolve Man with the Mark or AFD--which is a resiliency we sorely need.
3. Book of Eclipse has synergy with the Trap Monster line-up. Pumping out our Trap Monsters to interrupt the opponent first and then following up with Book of Eclipse actually resets the Trap Monsters (as they have the text "It's still a Trap") to be used later. This is obviously win-more, but it means that, in an intense grind-game, it is not as much of a liability as it might otherwise be.
Finally, the addition of Dragunity Remus and the sculpting of our hand trap lineup means Small World can bridge any of our handtraps into either Dragon Ravine (through Droll->Mulcharmy->Remus or Mulcharmy->Droll->Remus) or an Apophis Starter (Droll->Anubis->Man, Mulcharmy/Remus -> Droll -> Anubis, Nibiru -> Anubis -> Man) or even Serket if Treasures search is Ashed (Droll/Nibiru/Mulcharmy -> Anubis/Man -> Serket). That means, even though it takes a card, we can flex our non-engine lineup into starters or extenders as needed.
The Apophis typical endboard is the following:
1. I:P or S:P (depending on if you want to use your Apophis as material or not)
2. Divine Spirit of Apophis
3. Apophis the Serpent
4. 2x Apophis the Swamp Deity
This is around 2-3 pops/removal and two mass omni-negates on the field. This is a suite of endboard interaction that is particularly potent in a format that relies on monsters either on the field or in banishment. Spot removal is at a premium, and this deck ends on a healthy amount of it. This can be a problem against decks like Fire King that prefer to be destroyed, but it is possible to play around their destructions. EDIT: Previous versions were running Anguish Pattern as an end board piece, searchable off Silhouhatte. I think this is still defensible, but I wanted to play the most conistent version possible.
All in all, I'm very, very happy with list, and I invite you to try it out!