Fire bombs take quite a lot of health off him but you run out very quickly. Its easier to use electric breath when he crashes into the wall and ice breath when he sets off again. Ice shards are effective when he's driving about but make sure you have upgraded all your breaths to the highest level!
Submitted By charlotte100
Xbox
Kill Electric King Easily
Use your earth breath on its highest level on him until it runs out. Then, run all the way back to where you just killed Cynders Forces and wait until he does his special attack (when he surrounds himself in a purple veil) and he shoots down the purple spikes. Collect the gems the spikes release as they shatter until you have full breath energy. Repeat this until he is dead.
Submitted By mike savage
Xbox
Defeat Stone Sentinel Very Easily
Entry location:
Stone Sentinel Boss - Ice Dragon Rescue
First make sure your ice breath is at its best level.
Keep freezing him until your breath is half way down, then run up to him and triple tail whip him. When he spins around, freeze him and triple tail whip him again. Repeat this. When you are low on health, destroy the crystals surrounding you. Keep freezing and triple tail whipping him until you kill all three stages of him.