The Ullians were a humanoid race native to the Ullian homeworld. They were telepaths with a vested interest in learning the memories of other species, with the power to enhance and recover lost memories. (TNG: "Violations")
Before the 21st century, the Ullians were a violent people. Telepathic memory invasion was a common occurrence. By the end of the 21st century, they had become peaceful, and instances of memory invasion were virtually eliminated, although some members of the Ullian society still practiced that form of rape.
By 2368, the Ullians had embarked upon an ambitious plan to construct a library of memories from species across the Federation and beyond. Several Ullians, including Tarmin and Jev, were trained in telepathic memory retrieval and used the ability to reconstruct and collect memories. It was hoped the memory library would be not unlike an repository of oral histories. One group of Ullians visited eleven planets in eight star systems including Melina II, Nel III, and Hurada III. Kaldra IV was also a planned stop. Before the Ullian delegation arrived at Kaldra IV, Jev was found guilty of committing telepathic memory invasion against several members of the USS Enterprise-D crew, bringing a temporary interruption to the research. (TNG: "Violations")
For the most part, the Ullians were gentle, honest, and friendly people. They had a great passion for their work, but did not wish to coerce other species into participating if they were not willing.