If this card is Special Summoned from the Graveyard: Its ATK and DEF become double its original ATK and DEF. If this card destroys a monster by battle and sends it to the Graveyard: Inflict damage to your opponent equal to that monster's original ATK.
It works best with Dragon's Rebirth since it lets you special summon a Dragon-type monster from your hand or graveyard. Even if you don't summon from the grave, summoning from your hand can be good if you can end the duel with 1200 damage and your opponent can't stop your attack.
Castle of Dragon Souls helps with increasing a Dragon monster's attack by using Dragons from your graveyard as the resource, but its special summon effect won't activate Dragonblaze Dragon's effect since it's not from the graveyard. Reverse Glasses lowers your opponent monster's attacks so that you can destroy it with Dragonblaze Dragon easier, and the effect damage that you will inflict will still be their original attack.
Dragon Knight of Creation and Paladin of Felgrand are cards that are also released in the same structure box. These 2 help with special summoning level 7 or 8 Dragon-type monster from the grave, as well as getting them from the deck.
You can use Darkblaze Dragon as a fusion material monster for a fusion summon to send it to the graveyard. If your opponent negates or targets your fusion monster with a card effect, you can De-Fusion to special summon Darkblaze Dragon from your graveyard, which will activate its effect and can attack, plus your other monster that you used as the fusion material monster.