|This article is about a/an giant monster in Choudenshi Bioman.|
Grotescanth (グロテスカンス Gurotesukansu, 19 & 20) is a Mecha-Gigan of Neo Empire Gear, developed and utilized by Prince
Grotes Canth's greatest strength are its abilities to build and rebuild itself after its defeat and its "intestines" within its body, originally developed by Mason but used by Prince to constrict and attack Bio Robo after its been opened up
Grotes Canth is a secret Mecha-Gigan created and developed by Doctor Man's "son" Prince, created to assist him but using other of Gear's developments such as Mason's attack coils (initially used to suction gasoline from a tanker) for its usage. During an initial showdown with Prince, he summons the Mecha Gigan; Bioman appears to have an easy time dealing with it using Dashing Beam, but end up opening up and releasing the intestines, which attack it and constrict movement. Prince makes the battle all the more difficult by entering into the Mecha-Gigan to pilot it, making the team worry due to the belief that he was human. Eventually, the team use Super Maser to remove the intestines from Grotes Canth before it gets away; but Prince is forced to attack civilians until Bio Robo returns them to his creation.
By the time Bioman fight Grotes Canth again, they realize finally that Prince was a Mecha-Human and thus had an easier time fighting and attacking. Attacking the control module during the final showdown, Bio Robo defeats both Prince and Grotes Canth with ease, defeating him with Bio Robo's Weight Attack.
- Despite being a "Canth"-type Mecha-Gigan, its usage of a cockpit when Prince pilots the robot foreshadows the more mecha-like Neo Mecha-Gigan used by Doctor Man later.