Instructions
Equip your bow and arrow, as well as the Lens of Truth you have used throughout the Shadow Temple level as soon as the boss battle against Bongo Bongo begins.
Press the hotkey linked to the Lens of Truth to use the item's powers. The enhanced vision provided by the Lens of Truth will display both of Bongo Bongo's disembodied hands floating in mid-air.
Shoot each hand with an arrow. Avoid getting too close to the boss to do it; the closer you get to Bongo Bongo, the more your character will bounce up and down from the tremors his drumming hands create.
Shoot Bongo Bongo's eye after shooting his hands. The eye only appears after you shoot his hands and only when the Lens of Truth is active. Once shot in the eye, Bongo Bongo will fall to the ground.
Slash any part of the immobilized Bongo Bongo with your sword. After a period of time, Bongo Bongo will rise again and continue attacking you. Repeat the process by shooting his hands, then his eye. Move in close to attack with your sword. To defeat Bongo Bongo, you will have to repeat this process several times.