Monstroids are minor characters from the 1985 animated series She-Ra: Princess of Power, loosely based on the Monstroid from the Masters of the Universe toyline, but they don't look anything like the figure and it's unknown if they are related in any way to the Monstroid from the Sea of Rakash.
She-Ra: Princess of Power
The Monstroids are gigantic transforming machines that originated on Horde World.
He-Man and She-Ra: A Christmas Special featured several Monstroids that came from under Etheria's surface. They stole Orko, Miguel, and Alisha from Hordak and imprisoned them, saying that they would deal with Horde Prime when he came to collect the prisoners. The Manchines released Orko and the children from their cell, then helped He-Man and She-Ra fight off the Monstroids when they arrived.
The Monstroids reappeared in the episode "Day of the Flowers"; however, they were portrayed differently from their previous appearance. They were now working for Hordak instead of being independent, and they were also far less intelligent and rather easily destroyed.