Put the best of your dragons into the Battle Habitats of the Enchantment Arena.

 

You can set up your Battle Habitats by selecting the "Defenders" option on the main Enchantment screen.

Don't worry; these dragons will remain available for other purposes, such as fights or Gold production.

 

If your defense is strong, you can even climb higher in the Enchantment League just by letting other players get beaten by your impenetrable defense!