Forge an artifact 

Behold the Ancient Future Forge.
The holographic inscription repeats:

When mighty dragons gather,
Heroic hearts will merge
To forge an ancient artifact
With powers yet unheard.

Artifact rarity increases with the number of Dragons added. Minimum 3 dragons. 1 always remains yours, so eg. when adding 5, 4 will be merged and one will remain in your wallet.
The mint is FREE! (gas only).