The Levias/Bilocyte boss battle is can be easy depending on how well you can control Link’s Skywing. As soon as the battle begins, dive off the platform, call your Skywing, and fly towards Levias. Use the new spinning dash attack that Instructor Owlan taught you in order to destroy the four eyes that are hanging from Levias. Doing so will cause the Ocular Parasite Bilocyte to reveal itself; fly above Levias and dive onto his back to begin the battle with Bilocyte.
Take note of the wing-like fins on either side of Bilocyte’s head; as Bilocyte spits his green spike balls toward Link, use the master sword to deflect the balls back at Bilocyte’s fins. Once both fins are down, the parasite will open its eye widely allowing Link to either shoot it with an arrow, Skyward Strike it, shield bash a spike ball back, or deflect one more spike ball this time back into Bilocyte’s eye. Performing either action will cause the boss to drop to the ground where Link can attack with his sword.
Repeat this process once more and Bilocyte changes its pattern up slightly. This time, once its fins are down, the Ocular Parasite will attempt to dodge Link’s deflections. Remedy this by sending the balls in the direction that Bilocyte is leaning. Six shots in the eye later and Link will have rid the Great Spirit of the Skies of his worms, err parasite.