Where do you find Cores and Breedmarks in Game of Thrones: Dragonfire?

You get Cores and Breedmarks mainly two ways:

1. Chests (Hatchery, Conqueror's, event chests)
2. The Market, where the game sells rare / epic / legendary Cores in exchange for your surplus relics turned into Relic Shards

Both are permanent (they don't reset between reigns), so you can stockpile them from one season to the next without worry.

Buying strategy: since a Legendary Core 🟡 is only good on Legendaries and a Breedmark only on one breed, buy according to the dragons you actually field. There's no point buying a Legendary Core if you have no key Legendary to push: turn your shards into materials that match your real roster instead.