Mayahuel, the last Time Keeper, is Jin's mother. She's also an inventor, a golem and unintentionally the architect of the Lanthian Apocalypse.
Long ago, at the height of the Lanthian civilization, Mayahuel was a scientist or magician; however you wish to view it, she was a skillful inventor and engineer.
Her first accomplishment was making golems. She apparently invented the technology herself, yet we only know one golem she created, Tepoz. Her other notable golem was designed by her but actually executed by others: she taught Lanthian priests the art and they turned Mayahuel into a golem herself.
She was also involved in the making of the Calendar Machine and was one of the Lanthian VIPs in the mica-lined chamber when it was activated. The temporal anomaly left everyone in the chamber ageless and (as a side effect) aware of the time loops caused by the machine's malfunction; as it happened neither one was necessary for Mayahuel.
Foreseeing trouble, she took the Calendar Machine and left for the New World.
She was right; working without her, a group of Lanthian priests (probably with some overlap with the Time Keepers) made the Chimera.Centuries after the Lanthian Apocalypse a way was found to split the Chimera into the three Golem Girls. It seems shortly after that that Mayahuel tried to 'adjust' the Calendar Machine, getting sucked out of normal spacetime entirely.
She was unable to return to Earth, but watched from the Demon Realm as the world worked through 57 time loops. Mayahuel was able to make some contacts, under the right circumstances. About 20 years ago she appeared to a young Monica, presenting herself as Monica's great-grandmother and teaching the girl Glyph.Having to return Mayahuel to the human world was one of the goals that made fixing the Calendar Machine so tricky. Now that it's done she's living in Minneapolis and re-connecting with Jin.