Cerberus is an enormous three-headed rottweiler that guards the gate to Lord Agramon. You must kill him to open the door.
He's tethered (locked in place) but his aoe and disease spells hit at very long range. You can kill him with a single tank if the tank gets a lot of heals. Once you start whacking Cerberus his casting stops, but as you run up to him you'll take a lot of damage, so sprint to him fast.
For directions to the secret tunnel that leads to him, click here.
For information about other trophies that were introduced into the game at the same time as this one, click here.
In Greek mythology, Cerberus (also spelled Kerberos) guarded the gates of Haides. Here's what www.theoi.com says about him:
He was posted to prevent ghosts of the dead from leaving the underworld. Kerberos was described as a three-headed dog with a serpent's tail, a mane of snakes, and a lion's claws. Some say he had fifty heads, though this number might have included the heads of his serpentine mane.
One of the twelve Labours of Herakles was to fetch Kerberos from the underworld, which he accomplished through the grace of Persephone.
This trophy was
added to the game
in version 1.86 (the Labyrinth expansion) on November 14, 2006.