How do I get keys to open Hatchery chests?

There are three Hatchery keys, in increasing value:

• Dragonbone (the most common)
• Dragonglass
• Dragonfire (the rarest)

You mostly collect them through running events (reward tiers: besieging seats, spending gold/resources, daily login and so on), through leaderboards and in the Campaign. You can also open a chest directly with gold when you're out of keys.

Tip: save your best keys (Dragonfire) for the premium or event chests that offer Epic/Legendary Relics — that's where they pay the most. Don't open everything the moment you have a key: wait for a chest that targets the dragon you want to grow.