User blog comment:ChickenRave/Elmye, the Reflection/@comment-7709681-20150206183208/@comment-26030737-20150207151117

It's just not that simple, as Elmye has a limit of spells he can cast before they get blocked until he changes his form. People have to protect both physical damage and magic damage to resist him, but this champion has to raise AD and AP to stay efficient.

The Green Form is probably the most difficult to get rid off if you play full AD, because his spells need a target. The Red Form deals the most damage, however it's the only form that uses AD. Finally, Elmye must make every spell count in Blue Form since he gains more fury for each enemy hit, making the true damage terror last shorter than the other 2 forms.

You probably wouldn't have written this comment if you read with enough attention the second effect of Form Shift.