I will first say what are its attacks and what to do to avoid them and then i will tell how to circle it

In Top Left Keystone it will send a homing flame that chases ur styler. i recomend to circle it before the flame hits u
In Top Right has it shooting a diagonal energy beam that will take u a lot of energy. i recomend to avoid this by not circling him.
Middle has it creating dark shock waves around all the field so be careful while circling him.
Bottom Left has it shooting several shadow balls so don't circle him before he ends the attack.
Bottom Right has him create more flames circle him has u do in the Top Left.

U Can also use the drifblim and the electric pokemon help.