Murk is the forth beast Tom has to battle in series six (The World of Chaos).
Murk's blood red eyes can control people.He can also hide himself as part of the Rainbow Swamp, then surprise his victims...and consume them.
Murk suddenly rises up from the swampy mud of the Rainbow Swamp and hypnotize them. But Tom closed his eyes and, unhypnotized he started to attack Murk continuously but his sword slip through the beasts making no damage. Tom then lure the beast onto dry ground, hardening Murk and they defeat him.