You don't kill it you put it to sleep with the tune that the muse gives you in Apollo's temple.
The "gnarly monster" is Hydra, in the underwater cave in the realm of Poseidon. The other monster is the three-headed dog Cerberus in the realm of Hades.
Cerberus
To get to Cerberus you have to cross the river Styx.
In the Underworld-hell- as the guard dog of the god Hades.
the cerberus is a 3 headed dog on mythology island on poptropica
Cerberus is in the underworld past the River Styx in the realm of Hades. You will need a reed pipe (flute) and a song from the Temple of the Muses. Playing the short song will lull the monster dog to sleep.
In Poptropica's Mythology Island, the lullaby for the dog is a special song that you need to sing to calm Cerberus, the three-headed dog. To do this, you must find the correct notes to play on a musical instrument, which can be found in the game. Once you have the right melody, singing it will help put Cerberus to sleep, allowing you to progress in the quest. The lullaby is a crucial part of solving the challenges on the island.
You play the pipe tune and the dog will fall asleep. Then take the whisker.[Its one of the five sacred items.]
Monster Dog was created in 1984.
sorry you cant dont try otherwise they will kill you :(
The duration of Monster Dog is 1.4 hours.
if you mean in mythology island, you dont play a tune for the hydra thats only for the dog you have to jump on their heads if you need help just go to youtube and type in poptropica cheats mythology island