So, I got this description saying "Errored Gate Pearl, file a bug report detailing how you obtained this." I killed a mutant zombie which completed a quest "Slay Mutant Zombie" under the Lesser Evils questline playing the curseforge mod pack Cisco's Fantasy Medieval RPG [Ultimate]. If you have any more questions feel free to reach out

You'll want to report this to the modpack you're playing rather than here, since the pearl you're getting is being added by them.