At one point Gregorek along with his brothers, arrived in Portland and carried on there mass crimespree, breaking into people's houses and stealing there belongings. He was stealing from another house, when the son of the owner arrived home. Gregorek attacked him, the young man tried to defend himself but was easily over powered by the superstrong monster, who killed him with his teeth ripping his arm off. He then took the plunder back to his lair.
Either he or one of his brothers murdered a city sewer matience worker when he got to close to it. The deaths's allerted Nick and Hank, who after examing and discovering what they were up against, returned to the sewers to hunt down Gregorek. Finding his lair, Gregorek attacked them, overpowering Hank he attacked Nick. But coming prepared Nick was armed with a Vambrace (a arm protector, designed by his ansestors to hunt Galumcaedus, customised to include a special blade) and defend himself from Gregorek's bite. Hank recovered and holding him at gunpoint. They took him back to precinct, however Gregorek was confident he would escape. He was also somewhat impressed to meet a Grimm, or "Dēcapitāre" as was there old name (latin basically meaning one who decapitates)
Later his brother Andre kidnapped Hank, and forced Nick to bring Gregorek to him or he would kill Hank. Taking Gregorek back to there lair, Nick was forced to come alone and leave his gun behind. Gregorek revealed amongst his kind the Dēcapitāre were greatly respected, and his grandfather told him stories of them to scare him, though he didn't find him that scary now. Arriving with Hank, they made the switch, however Gregorek told Andre what Nick was and they agreed to kill him. Hank managed to warn Nick in time there was a third Galumcaedus. Nick fought him off, while all three brother joined the frey. Still armed with his Vambrace Nick killed Andre and the unnamed brother, but Gregorek caught him into the wall. The two began to struggle purely on strength. However Hank broke free and hit him round the back with a pipe. This was enough for Nick to defeat him. Defeated, Gregorek was horrified at Nick killing both his brothers. He was presumably arrested for his crimes.