For that, you're getting literal free mana since the card has no mana cost but taps for mana, so long as you control a dragon
The idea that intrigues me there is Cauldron of Soulsyou could cast a battlefield wipe on your turn and then attack with your slightly smaller team without resistance
In an aggro deck, you wont find many cards with a high mana cost, and as a result, most cards wont be super powerful or game-changing on their own
As you saw in this week's title, I have drawn the Gruul straw
Nahiri goes upto 6 loyalty with a +2 on the turn you make her if looting, this makes her incredibly hard to deal with
If you have more than two instants or sorceries in your graveyard when this resolves, you get added to your mana pool, making this essentially a Demonic Tutor