Had the idea of a Spawn of Tiamat, they somehow was taken from Tiamat's lair before the Dragon Queen would devour it.

It's been stated that Tiamat is able to very rarely create a true five headed offspring amongst her many litters she carry, but never allows these true-spawn to live long, eating them when discovered, as she fears their potential - Which would imply that the true-spawn of Tiamat could grow to easily surpass the Queen herself in power, status and strenght.

What if a team of heroic adventurous braved the very lair of the Dragon Queen, in the 1st layer of the abyss itself - Rescuing a True-spawned Egg and carrying it to safety on the material planes to raise it themselves - In the knowledge of goodness, compassion, truth and selflessness.
No single creature (other than Planar incarnates - like devils, elementals and demons etc) are truely bound to any alignment, even one born as a Spawn of Tiamat (who became a devil, not truely one). It would be no different than say, a Tiefling with their infernal heritage, still being absolutely able to be good, just and kind.

This spawn of Tiamat, would become the Dragon Queens greatest enemy, surpassing even that of Bahamut - As it would be a reflection of self, and the promise of redemption that the Queen of Greed could never accept.

Anyway.

Cute Spawn of Tiamat with a stat block I drew up while it was quiet at work today.

-Gamal