1. After reading about all of the synergies that Frost and Flame Dragon has here, you might be confused to see that I'm only running one copy. Why is that? Well, to put it bluntly, it's a lot harder to summon than you'd expect, even in a deck specifically made for it. And when it does hit the table, it's not exactly a game-ender - sure, blowing away monsters is cool, but 2300 ATK and no other effects will not win the game on its own. (Usually, this deck wins by punching people in the face with Tidal or Blaster repeatedly.) Also, this card is sadly not Level 7, so drawing extra copies can't even be leveraged into a Sacred Sword.
I decided that completely eliminating the chance of drawing multiples (while still keeping the card as an active late-game threat since I can search it whenever I need it) is the best way to go. It's easier to think of this card as simply being the reason why this deck was created instead of the reason why it survives.
2. Hydrogeddon is a card that hasn't seen much mainstream play in many years, but here it's very good. You'll see that some of the monsters in this deck share a recurring theme of grabbing other monsters from the deck - this was my idea to fill the graveyard with targets for Frost, Tidal and Blaster without running too many Earth and Light monsters like Card Trooper, Magical Merchant or any Lightsworn that instead share a goal of randomly milling them. (If I had to guess, I'd say you can definitely run a build like that; it just doesn't fit my personal taste.)
In addition to pulling extra waters from the deck, a single Hydrogeddon can turn into the two Waters and one Fire you need to summon Frost and Flame Dragon - by overlaying to summon Evolzar Laggia or Dolkka! I wish I would've taken a picture of my face when I first figured this out.
3. To explain the other Water monsters, Mother Grizzly follows the theme of recruiters. It also can search out Skreech, who adds a lot of speed to this deck by immediately dumping two Tidals into your grave. Blizzard Dragon is one of the only playabale standalone Water Dragons I found, but it carries its weight beyond just its typing. 1800 ATK is pretty decent and its effect can be surprisingly useful.
4. The Fire monsters are all simple to understand. Masked Dragon is another recruiter, but even better than Mother Grizzly since Blaster can search it and it can summon its targets in Defense. Dread Dragon can also search Masked Dragon, but I normally use it as a doubly-searchable Level 2 Tuner. Flamvell Guard offers a similar role, but at Level 1 instead.
5. Triple Lance is very potent in this deck for its synergy with Hydrogeddon, as well as its ability to make sure your boss monster summons break through. Double Typhoon helps to accomplish a similar task while also getting rid of any annoying face-up backrows.
6. The last notable main deck card is probably Dragoncarnation. Once this deck gets rolling, it banishes a LOT of monsters. I ran Return when I first started with this deck, but it kept getting stuck in my hand doing nothing until the late game. As far as taking advantage of our banishing habits, I've found Dragoncarnation to be a much faster, safer option that gives you a useful bit of refueling, rather than trying to drag you into the apocalypse.
So that's all for this deck profile! If you guys have any suggestions, I would love to hear about them down in the comments. Thanks for reading, and I'll see you later.