Charge a Treble Energy Bolt, and shoot it at one of his shields (hands). He will show you the opposite "elbow" (flashing red) of the shield you shot. For example, if you shot the left hand, then he will show right elbow and vice versa. Charge a Single Energy Bolt, aim very carefully and shoot it at the elbow which he showed you. If you hit the elbow, the shield will explode. Immediately after that the ST will open a cannon (flashing red) located in his head. Shoot this with a Single Energy Bolt. With the destruction of one of his shields and his head, you will seriously damage him (nearly 70% of his energy will be gone). If you miss the shot to his elbow, simply charge a Treble Energy Bolt and start again. It is very hard to hit it because it trembles a lot.