Source: Endless Night, pg(s). 51
Mardeis Parastric is not just the daughter of the powerful matron Astranovidova Parastric but she is also her bodyguard and a selling tool as Mardeis is not a drow like her mother but a fleshwarped creation known as a drider. House Parastric, the noble house to which Mardeis belongs, are worshippers of Haagenti the demon lord of alchemy and change and thus specialise in the creation of monstrous beings that serve the drow, they do this using a process called fleshwarping. So dedicated to Haagenti was Mardeis's mother that she had her own daughter turned into a fleshwarped creature, now she travels with Mardeis using her as both a bodyguard and as a demonstration of House Parastric's flesh warped creatures, which they sell to other drow houses.