The mother grub is a monstrous being who lives underground on the planet Alternia. She gives birth to all trolls from a mixture of the genetic material of all adult trolls, delivered to her by Imperial Drones from filial pails. She combines all the genetic material into one "diabolical incestuous slurry" and lays hundreds of thousands of eggs at once.
Only the Solar Sweeps ago, has been seen. However, the skull bears an to Kanaya's Lusus; this is because her lusus is a Virgin Mother Grub who declined to brood and instead become a lusus naturae. Other than an extremely shortened lifespan, it is unknown what other biological differences result from this distinction.of an ancient mother grub, slain thousands of
According to Karkat, they have an “OOZING VESTIGIAL THIRD ORAL SPHINCTER”.
The Matriorb was later brought back by Roxy Lalonde and handed back to Kanaya, so she could hatch the new mother grub.
A new Mother Grub is hatched from the Matriorb given to Kanaya by Roxy, as seen in the MSPA Snapchat. The new Mother Grub has been shown to continuously produce more broods of trolls throughout its lifetime.