The Stone Dragon is raised in your second outpost and will protected it. You have to upgrade the Dragons Keep to evolve your Stone Dragon from egg to adult.
In order to build the Stone Dragon Outpost, you must obtain the egg by attacking level 7 and up hills with a Great or Elemental Dragon included. It is recommended that you send 2 waves without the Great or Elemental Dragon and on the 3rd wave include the Dragon. This will keep your Dragon from taking excess damage and long heal times. For more information on obtaining eggs, please visitGetting Eggs. After you have obtained the Stone Dragon egg and a plain, you can now create the Outpost. For more information on Outpost, please visit theOutposts page. This Outpost is similar to the Water Outpost, except this one will allow players to train Granite Ogres when they meet the prerequisites. When your dragon's keep is at level 8 and you have obtained theStone Dragon's armor, you will be able to include your dragon in attacks.