The Amnesiac Mermaid Game Over is an ending which occurs when losing to the Sea Witch in the Mermaid Caves.
After the battle, the recall spell teleports all party members except Eric(a) away, leaving him (now her) alone with the Sea Witch. The Sea Witch wipes her memories when she tries to resist. Upon realizing Eric(a) has forgotten almost everything, including name and identity, the Sea Witch decides to shelter her from "that bitch of a princess", giving her the name Nadia after the Witch's deceased sister. She also introduces herself as Allura.
The Witch takes her away to safety, starts a new home and decides to train her as an apprentice. During this period, Eric(a) is frequently molested for Allura's entertainment. After a while, Allura finds a village of humans and is impregnated by a man there. Eric(a), not wanting to be abandoned, asks to be part of her new family, becoming Allura's wife and taking on her fertilized eggs.
It is stated that Eric(a) is happy with the ending, despite the prospect normally being horrifying. Memories of Wendy occasionally resurface, but Eric(a) dismisses them.