The Department of Temporal Investigations is a Federation agency that looks into whether time travel incidents within Federation jurisdiction were handled properly, to avoid contamination or changes to the timeline.
The dour (but comical) duo of Dulmur and Lucsly first appeared on Star Trek: Deep Space Nine‘s episode, “Trials and Tribble-ations“. Although that was their only appearance on screen, they have seen action in novels and short stories since.
Below is a version of Dulmur and Lucsly as Notable NPCs that you can bring into your game. Most likely your players will first encounter them after they finish a time travel misadventure, but Dulmur and Lucsly can also be brought into missions that involve time travellers that have arrived in the 24th century, or artifacts that allow travel through time. Feel free to adjust their stats and focuses from appearance to appearance, especially if your players contaminated the timeline in the previous adventure. As a version of Dulmur once said (or will say), “For all we know, we could be living in an alternate timeline right now.”
Have fun with them – my players had just finished an encounter with a time loop and a time travel incident, and I’m looking forward to having them meet Dulmur and Lucsly myself.