How do you raise a dragon's Star Rank in Dragonfire?

A dragon's Star Rank only goes up by stacking its own relics (Hatchery). No gold, no resources: it's the relics of that exact dragon that make it grow.

The known costs climb steeply:

• 1★ (hatching): 15 relics
• 2★: 40
• 3★: 100
• 4★: 180
• 7★: 800

5★ and 6★ aren't confirmed yet (the curve can't be deduced without them). The good news: Star Rank is permanent — it never resets between reigns. Every star you buy stays yours for good, which makes it one of the best places to put your relics.