Legend has it that Argus, a monster with a blue body that is covered in eyes, is weak against the Serpent Staff.
A giant with a hundred eyes on its body. Keeps track of its surroundings with ease. Its eyes take turns sleeping one half at a time, allowing it to essentially stay awake constantly.
--Vita version bestiary
Argus is a Sub-Boss of the Surface. It is a blue giant that roams Surface (B-3). He constantly moves towards the player to crush him. Until you get the Serpent Staff, Argus is invincible. Projectile weapons of any sort will pass right through his legs, so you must jump and throw to defeat him. Once he is defeated, the way to the Feather is open for you.
The Serpent Staff is required to damage Argus.
As soon as you enter the room, Argus will march toward Lemeza from the left. If he isn't killed quickly, he will run into Lemeza and knock him out of the room. When you re-enter, Argus' health resets and he starts marching again from the left.
With Serpent Staff equipped: Torso, head
You don't have to use the Serpent Staff, just equip it.
Quickly attack Argus with your Whip. If you take too long, Argus will win the fight by knocking you into the next room. Run a little ahead of him, so he will walk into position for when you jump.
- 4 hits from the Chain Whip kills him.
In Greek mythology, Argus Panoptes or Argos, guardian of the heifer-nymph Io and son of Arestor, was a primordial giant whose epithet, "Panoptes", "all-seeing", led to his being described with multiple, often one hundred, eyes. -Wikipedia