Started out trying to make a relatively cheap dragon deck and ended up with a lot of fun interactions.
You start with innate defense in the amount of Dragon Eggs and Smoldering Egg
s.
There are also cheap little Dragon Hatchlings and, of course, Dragonlord's Servants to pump out all your dragon critters quickly. Get Scourge of Valkas onto the battlefield and then you're prepared for total opponent annihilation.
Valkas' ability of, "Whenever this or another Dragon enters the battlefield under your control, that Dragon deals X damage to target creature, player or planeswalker, where X is the number of Dragons you control," gets out of hand when you have fodder on the playing field then drop a Descent of the Dragons. Sacrifice your Dragonlord's Servants first, and replace them with 4/4 dragons, increasing the number of dragons on the battlefield. Each time you do this, Scourge of Valkas' ability triggers. Sacrifice Dragon Eggs to gain not even the 4/4 tokens, but 2/2 tokens since the card reads, "When Dragon Egg dies, create a 2/2 red Dragon creature token with flying and 'R: This creature gets +1/+0 until end of turn.'" It's up to you if you'd like to sacrifice the Smoldering Egg
s as you could end up transforming them to 4/4 dragons anyway with the additional ability of, "Whenever you cast an instant or sorcery spell, Ashmouth Dragon deals 2 damage to any target." You won't get a ton of use from that ability, but it can be useful especially if the sideboard comes into play against decks you want a little extra protection from. Regardless, at this point, you've now created an arsenal of dragons all of which, individually, triggered Scourge of Valkas' ability each time they entered the battlefield. Now imagine if you have two Scourge of Valkas out, which will EACH allow that to happen to EACH dragon you're creating.
If you have even a handful of fodder out ahead of time and cast Descent of the Dragons with Scourge of Valkas out, you can one-shot your opponent. And, if you don't one-shot them, then you have plenty to strike with, especially if you get out Crucible of Fire to make everything giant. Crucible of Fire is great out early even on your fodder, too.
Sarkhan's Triumph helps you ensure Scourge of Valkas is out, or it can help you continue to gather fodder for a more potent Descent of the Dragons. Fires of Invention creates a nice interaction with Dragon Roost as then you you can pump out two 5/5 dragons for the mana cost of 1. You don't want to handicap yourself though by putting out Fires of Invention too early and preventing yourself from casting multiple things, such as an arsenal of fodder on the same turn. It's definitely a mid- to late-game card. And lastly, Dragon's Hoard helps keep cards in your hands to keep filling the battlefield and keep the mana flowing.
