Once the battle begins, collect any hearts around the island you may need. You can also use this place for some health restoration when needed. Afterwards, dive off the edge and call your Loftwing.
Once you do, the battle begins. It is actually quite simple – there are four eyes trailing behind Levias. You are to Spiral Charge into all four.
The bad thing is that this battle is pivotal primarily based on your control of a Loftwing (which is hard enough in this game when you demand accuracy).
Then there is the fact that Levias is about as fast as you, so if the tail or eyes’ optic nerves hit you, you lose a heart.
I tend to try to approach Levias from the side. He is generally circling during this battle, so I kind of make a chord in the circle to beeline for where his tail end will be. Then I try to Spiral Charge an eye and repeat.
The battle ends once you eventually hit all four eyes.
After this, a creature emerges from what could be Levias’s blowhole. Fly above Levias and slowly descend towards the lighter portion of his back, then dive onto it, tilting forward for the utmost accuracy. Upon a successful landing, this boss will begin.
During this battle, the Bilocyte’s primary means of dealing damage will be to shoot green orbs of poison at you. Begin by moving to around the middle of the platform.
There, you are to counter the orbs by swinging at them with your sword. Hit one with a left-right horizontal slice, and another with a right-left horizontal slice, to hit the boss’s head wings.
After damaging both wings, hit another orb vertically to stun the boss, then go up to it and bash it with your sword.
Repeat the above process and deal enough damage to the eye to continue.
For the second phase of the battle, move as far away as possible from the boss. It will continue to throw the yellow orbs at you, but also will move after shooting the orb.
Using the same “physics” as before, hit the orb at the head. You can continue to do this for a while.
Alternatively, since your Master Sword has a long range with the Skyward Strike, you can attack it directly with those. However, that would put you in more danger, but it would end the battle quicker.
Okay, then. After the battle, Levias will finally regain control of himself. Speak with him and you’ll learn some more about the Triforce, but still not its actual location.
To find it, you need the Song of the Hero. It was broken into four parts, which are held by four dragons: the Water Dragon, the Fire Dragon, the Thunder Dragon, and Levias. You need to visit each of them (Levias is the last) to find the proper portion of the song.
At this point, you can head to any of the three locations: Faron Woods, Eldin Volcano or Lanayru Desert. For convenience, we’ll head to Faron Woods first.
Anyhow, exit the Thunderhead and head further southeast to the Faron Woods. Land within the green light beam, as per usual. Descend in the Sealed Grounds.