Reptiles got an in-theme reborn, so of course we're going to be abusing it.
Third Coming of the Reptilian Count can special summon any Reptile monster from your grave, which includes effect monsters. As such we can summon Ecdysis Caliguleon, the strongest Reptile boss monster available. Caliguleon can hit very hard given setup, and is a lot easier to use compared to the other available targets. 1 Predator Gunleon is also ran as a toolbox option, if you're at the position where you happen to be at the lifepoint threshold necessary, or can force yourself to that point, Gunleon is a very good choice. 3 Alien Count of the White Dwarf, St. Germain as really the target of choice for the 3 Secret Order in the deck, but you can theoretically get it off of Third Coming if you don't have other options. 1 Clawleon is also in the deck as another toolbox option, this one is here to help you finish games by giving your monster piercing. Since Third Coming does not care for level, if you are in the right position it is a good tool to have.
We still need Level 3 or lower Normal Reptiles for the cost of Third Coming, so we've chosen 3 The Three Warp-Granny Sisters and 3 Yormungarde as the highest attack options, and 3 Sannomiya Golden G Robo MK-III as the highest defence option over another beater as there's enough beaters for me. 3 Sickleon to mill out the deck, pay lifepoints and potentially get tribute fodder to your hand. If given the option you can also choose to add St. Germain as a 2 tribute monster if you need more of those at any given time.
3 Ship of Seven Treasures, 3 Amazing Dealer, 3 Enraged Scale Liberation and 1 Graceful Charity are your other consistency pieces in the deck. Enraged Scale Liberation can set up your graveyard dependent cards and also pay lifepoints for a Gunleon play. I've still not really settled on a Legend card right now, Monster Reborn is not needed though given you already have 3 copies of an in-theme one. 1 Aegis of the Five Houses as a way to protect your Caliguleons and Gunleons from cards like Mirror Force or Vacua Annihilation. And finally 3 Magical Stone Excavation to abuse and recycle all these spells.
Overall, the deck can go very fast, special summoning high attack monsters, milling through their deck and even having toolbox capabilities. If you want to play a deck that plays very fast and loose, this deck is for you.