This mode will allow you to customize a base with any level defenses,walls,Ect.You can also use any troop and any level.With this mode you can try out new strategy's,Build your active base, attack your base and see how good your base is and see how you can improve your base.Also in Clan Wars when there is a certain person you are going to attack, then in the Custom Mode build that persons base and attack it with your level troops and see how you can improve your attack.This Custom Mode would be great to try out strategy's,Bases and much more!