Lust for Darkness (Spoilers)
2 years after Jonathan rescues Amanda, she gives birth to their second child (their first child was forcefully aborted by Willard Yelverton). Jonathan checks in on the child before returning to Amanda. By the time he reaches her, Amanda has opened a portal to Lusst'ghaa and invites him to sex.
Lust from Beyond: Prologue (Spoilers)
By time of the Prologue, just two years after it was born, the Child is a fast and brutal monster, larger than an adult human. It seemingly serves its mother, Amanda, who sends the Child to the new mansion of the Cult of Ecstasy to bring her Christopher.
Lust from Beyond (Spoilers)
The Queen of Ecstasy side stories reveal that Amanda tried to live a normal life after Jonathan rescued her, but her growing sexual frustration, along with (possibly empowered by) her Seeing visions, eventually drove her to sacrifice her child to open a portal into Lusst'ghaa in an effort to sate her sexual urges. The ritual involved slitting the child's upper lip and offering it in prayer to the Lustful God. The ritual was successful and a portal opened, after which Jonathan arrived and Amanda broke him with sex (the ending scene from Lust for Darkness).
The Child, affected by Lusst'ghaa's energies, grew quickly into a monstrous, tall form with a tail. Its face sports a hole with the upper edge slit, reflecting how Amanda slit her child's upper lip to open her first portal into Lusst'ghaa. Amanda notes how heartbroken her husband was upon seeing what their child became.
While Victor is searching for Ughro'ecna's mask, Dominic and Donald discover Amanda had been hiding the truth about Xu'thrar; it is, in fact, a prison, not a technological hub that will heal Lusst'ghaa. They rebel against Amanda, but Amanda summons her Child into the Mansion. As happened during its first attack, the Child wreaks havoc on the Mansion's inhabitants, killing or severely injuring them. In particular, this is Mabel's and Theodore's second encounter with the Child; Mabel recognizes it from before and is again severely injured.