The Four Artificial Spirits from the original Monster Girl Quest trilogy created by Promestein makes a return in form of skills.
Overview
In the original timeline, these four spirits were mass produced by Promestein and used to power up entrusted monsters, enhancing their skills and abilities in hopes of defeating Luka. You can get these Artificial Spirits through a certain Job.
Trivia
It is unknown whether the alternate version of Promestein re-created them in this timeline, as her location is currently unknown or whether she is traveling around, but rumors of someone with a white coat is spreading...