Tempore Ruga  is a ghost with the power to fold space-time.
In an alternate 1984 timeline, the Ghostbusters captured Tempore Ruga at sometime before their first battle with Gozer. Due to its time manipulating powers, Egon Spengler and Ray Stantz decided not to store it in the Containment Unit out of fear it could still use its powers and let other ghosts escape. They planned to build an isolation unit to store it but never got around to it.  For 31 days, Tempore remained in a Trap in the Firehouse. After Gozer came to them for help returning to its home dimension, the Ghostbusters spent a hour of painful and unproductive brainstorming. Egon and Ray eventually realized they could use Tempore and convince to help with the threat of retrapping it. They released Tempore but he didn't recognize them at first. He didn't seem interested in helping them out as a thanks for letting him go. Winston Zeddemore pointed out they released him into a world ruled by the Stay Puft Marshmallow Man and its Mini Pufts. Tempore was horrified and agreed to assist them.
Anticipating betrayal, Egon told Gozer to meet them at the Temple of Gozer because they could minimize potential errors by generating the temporal fold at the portal. They went back in time and plastered the Temple grounds with posters of an animated character named Loofajoe Rectangleshorts. This would serve as a precaution against Gozer. Back in the present, Tempore instructed Gozer to concentrate on the precise moment in time where it needed to go back to then it flew into Stay Puft's head. Gozer found itself back in the middle of its initial battle with the Ghostbusters.
Tempore Ruga appears in the form of an Old World European gentleman.
Tempore is a powerful specter with the unique ability to create a kind of temporal fold, literally fold time turning it back. Essentially, it could send someone back in time. 
- Tempore Ruga's name roughly translates to "Time Wrinkle"
- Egon Spengler (2016). IDW Comics- "Ghostbusters: Deviations" (2016) (Comic p.13). Egon Spengler says: "But we never put Tempore Ruga in the Containment Unit."
- Ray Stantz (2016). IDW Comics- "Ghostbusters: Deviations" (2016) (Comic p.13). Ray Stantz says: "We feared that contact with other spectres might allow it to use its temporal fold powers on them, allowing them to escape. We planned to build an isolation unit, but we hadn't gotten around to it."
- Ray Stantz (2016). IDW Comics- "Ghostbusters: Deviations" (2016) (Comic p.12). Ray Stantz says: "Regardless, it's reported that the spectre can create a... temporal fold of sorts. It can literally fold time, turning it back. Essentially, it could send something back in time."