He is already in the game, it would be easy to work in. remember being attacked at the beginning of the game?
Upgradable Just as Barb King and Archer King, available at TH9 or TH10
Glorified goblin, only attacks resources, tons of HP and DPS.
Just as goblins are the fastest troops in the game, his hero power would be lightning speed, or something along those lines.
Idk, you can work in a story about how he switched sides if you want, maybe you would have to complete the single player missions and take him captive or something.
