The Dragon Den allows you to sacrifice, level-up, evolve and prepare your dragons for battle. This is where players select which dragons they want to bring to each raid (up to 3), and where they sacrifice and evolve them. If the player has less than 3 dragons, all of his dragons are automatically selected. The Dragon Den does not upgrade past level 1.
Dragons that are vanquished during raids return to the Dragon Den with 1 hitpoints. Dragons that are hurt will self heal. Healing will take some time (depending on the dragon’s life) but players can skip this healing time by spending Amber.
Evolving: Players can evolve their dragon in the Den. See the section about Evolving for more detail on the mechanics.
Sacrificing: Players can sacrifice their dragons to generate Essences. See the section about Essences for more detail on the mechanics.