Kottus is one of the The Centimani, archaic giants of great strength said to possess 100 limbs and hands.   This as we see in the Hammer of Argus is in fact, an exaggeration, as Kottus and the rest of the Centimani have 10 arms–but whose strength is so vast that they are said to have the strength of 100 arms and hands.

They were the eldest children of Gaea and Uranus, The Earth and Night Sky. They were known as Briareus the Vigorous, Kottus the Striker (or the Furious), and Gyges (or Gyes) the Vast-Limbed.

Soon after they were born, their father, Uranus, viewing them as deformed and hideous, cast them into the depths of Tartarus.

The Centimani were later joined by their brothers the Cyclopes in Tartarus, and all of them guarded by the dragon Kampe, until thousands of years later they were rescued by Zeus to aid him in the overthrow of Kronus. In the ensuing war with the Titans, the Hecatonchires threw immense stones, as big as mountains, at the Titans, and overwhelmed and buries many of them. After the war,  The three Centimani became the guards of the gates of Tartarus.

Eventually Kottus became weary of his position as jailer in Tartarus, also over the span of thousands of years started to become corrupted by the evil that he held guard over.  Rather than an honor, he eventually considers it just another form of imprisonment by a group of deities who feared their might and power.  He began to conspire with the deposed Titan king Kronos.  Kronos agrees and quietly Kottus began freeing some of the denizens of Tartarus on the agreement that their souls would be rewarded for helping overturn the Olympians rule.  He also began employing the restless spirits of the unburied dead, to spy for him in the mortal plane, promising them rest and reward as well for their assistance.

It was Kottus which released Tantalus and Ixion to hire Brutus Starslayer to steal the eye of Elysium.