After Grebnedlog had asked for repair assistance, he captured Chief Engineer Geordi La Forge and held him hostage. The Pakled got their technology by stealing it from other species, so Grebnedlog informed Commander Riker that he would release La Forge if all the information from the Enterprise-D computer were transferred to his ship. After La Forge managed to disarm the Pakled's on-board weapons, Riker threatened to destroy them and faked the destruction of their weapons by means of a crimson force field. Grebnedlog, impressed by this force field, released La Forge because the Enterprise-D was "strong". (TNG: "Samaritan Snare")
Background information Edit
Grebnedlog was played by actor Christopher Collins.
Writer Robert L. McCullough explained the names of Grebnedlog and his subordinate Reginod: "These were names I learned in junior high school," McCullough explained. "My last name used to be Goldenberg and my best friend's was Donager, and we had a code of calling each other by our last names backwards." (Starlog, issue 187, p. 54)
"Greb-NED-log" was the pronunciation of this character's name from the script pronunciation guide. 
The short story A Dish Served Cold is about Grebnedlog's quest to get assimilated by the Borg in order to get revenge on Riker and the Federation. After his assimilation, his Borg designation is Auxiliary Adjunct 9 of 9.