The DC Breeding Sanctuary is a new feature added by Social Point. There is primarily 5 levels of different dragons you can unlock to breed. You will need gems though. To unlock the level 1 sanctuary for breeding, you will need 25 gems.
This is only available after you have reached level 25. Upgrading the sanctuary costs gold or gems.
Level 1 – 25 Gems
Level 2 – 90 Gems
Level 3 – 120 Gems
Level 4 – 180 Gems
Level 5 – 280 Gems
Below are the dragons you can breed:
Level 1 – Deep Red, Wizard, Ninja, Burning
Level 2- Wizard, Steam, Quake
Level 3 – Dujur, Gargoyle, Magnet, Apocalypse
Level 4 – Blue, Glacial, Howl, Promethium
Level 5 – Meteor, Forge, Abyss