The Ghostmakers are a legion of red demons that exist in an extra-dimensional realm accessible by mirrors and other reflective surfaces. They are led by the Mirror Demon. He decided it was time to take over the human realm and sent his Ghostmakers to possess humans.  When a human stares a transformed mirror, the Ghostmaker can enter the human's body and eject their soul, rendering it invisible and inaudible to the living.  Essentially they become ghosts for the lack of a better term. The first known Ghostmaker appeared at the Hardenbauer residence and possessed Mr. Hardenbauer via a mirror.
While the Ghostbusters investigated at the behest of Mrs. Hardenbauer, Eduardo Rivera was next to be possessed. In the Firehouse, the possessed Eduardo then had Slimer possessed by the rest room mirror. While investigating a possessed couple in upstate New York, the Ghostbusters discovered they gave off P.K.E. readings and pursued them in vain. During the chase, Garrett Miller was possessed as well and walked upright. At the orders of the Mirror Demon, the Ghostmakers proceeded to take care of the Ghostbusters. Eventually, the entire Ghostbusters staff were turned until only Kylie Griffin remained. Kylie's only hope was one of Egon's experimental devices, the Mass Makers. Kylie convinced the possessed humans that she was possessed as well and used the device to make all the souls visible and audible. The souls re-entered their proper bodies and the Ghostmakers were trapped. After all of the team were restored to their bodies and the entities trapped, they most likely returned to the Hardenbauer's and the other couple to exorcise them. The threat of the Ghostmakers ended forever once Eduardo trapped their leader.
Ghostmakers have the power of possession. Once in a human host, they have a unique range of powers: the ability to transform mirrors or reflective surfaces into portals, increased strength and speed, and any deficiencies such as paralysis or near sightedness are corrected. They can outrun regular humans and strong enough to punch a hole through a wall after a few hits.
Also, it should be noted that whenever they possess humans, they have an odd tendency to pause between words when they speak. The victim's soul must be returned to their body if the Ghostmaker is extracted or else the body is rendered dead.
While in human bodies, the Ghostmakers still give off a high P.K.E. readings. *Eduardo hates mayonnaise. 
- ↑ Egon Spengler (1997). Extreme Ghostbusters- The Ghostmakers (1997) (DVD ts. 12:44-12:47). Sony Pictures Home Entertainment. Egon says: "We're dealing with Ghostmakers."
- ↑ Garrett Miller (1997). Extreme Ghostbusters- The Ghostmakers (1997) (DVD ts. 09:42-09:45). Sony Pictures Home Entertainment. Garrett says: "These Mirror Demons keep us out of our body, right?"
- ↑ Mirror Demon (1997). Extreme Ghostbusters- The Ghostmakers (1997) (DVD ts. 04:05-04:22). Sony Pictures Home Entertainment. Mirror Demon says: "Comrade, the human realm will soon be ours. Join the others who have emerged and transform all mirrors into portals so we may continue to claim human bodies as our own. But first you must eliminate any threat impediments."
- ↑ Egon Spengler (1997). Extreme Ghostbusters- The Ghostmakers (1997) (DVD ts. 12:41-12:43). Sony Pictures Home Entertainment. Egon says: "It's more likely the demon inside has ejected Garrett's spirit."
- ↑ Roland Jackson (1997). Extreme Ghostbusters- The Ghostmakers (1997) (DVD ts. 06:59-07:01). Sony Pictures Home Entertainment. Roland says: "W...what? They're giving off something fierce!"