Putting the creature straight into play is what really makes this card powerful, and you might get some value out of sacrificing a creature depending on how you built your deck
And with black mana around, the player will probably have access to reanimator effects like Bladewing the Risen to get back some of those fallen Dragons
Equipment that can become creatures have the reconfigure ability, which lets you pay a mana cost to switch between modes.
Because I know these are questions people will have, or mistakes people might make: No, you cant find a colorless creature with this if your legendary creature is colorless
The D23 promo version of Maleficent, Monstrous Dragon, and every other promo from the event are likely to maintain their value over time, making them solid investments if you happen to have a few in your collection.
Locking down someone's commander and turning off its abilities can sometimes be better than straight up removing it all together