Mantocefalus

The Mantocefalus are gigantic mantises that guard the Breath of the Ocean. They live on the Island World, a star-shaped island currently above the Infinite Ocean.

Appearance
Mantocefalus has the appearance of a normal praying mantis, but they are, however, three times the size of one.

Season 5
The Mantocefalus appeared only in "Saving Paradise Bay" where they attacked the Winx for trying to obtain the Breath of the Ocean so they could save Paradise Bay from being polluted by Tritannus.

Magical Abilities
Mantocefalus has the ability to disappear and appear again, along with teleporting themselves. Just like the Wizards of the Black Circle, they seem to be immune to fairies' magic, as the Winx's spells do not affect them.

Trivia

 * The name Mantocefalus means "Mantis Head" and comes from Mantis, the name of an insect, and "Cephalicus", which comes from the Greek word Kephalē (κεφαλή), which means "head".