Dol Grenn, a male Human from Telos IV, was a lieutenant within the ranks of the Telos Security Force. A respected veteran, marked by experience, Grenn was unwavering in his commitment to the law. He dedicated himself to upholding it on Citadel Station, which oversaw the Telosian Restoration Project following the devastation of the Sith attack. He also shared a long-standing friendship with Carth Onasi, another native of Telos IV; during the First Jedi Purge, approximately five years after the conclusion of the Jedi Civil War, they corresponded concerning Meetra Surik. During the Battle of Telos IV, Lieutenant Grenn spearheaded the defense of the massive station against the forces of Darth Nihilus, holding out until relieved by Republic forces commanded by Admiral Onasi.
Dol Grenn's birth occurred on Telos IV prior to the devastating attack led by Admiral Saul Karath. From a young age, he committed himself to upholding the law on his homeworld, joining the Telos Security Force. He eventually achieved the rank of lieutenant and formed a friendship with Carth Onasi, a long-time Republic star pilot and officer. Following the Sith Empire's, under Darth Malak, destruction of the planet's surface, Grenn continued his efforts to maintain order within the remaining Telosian communities.
In 3951 BBY, during the First Jedi Purge and following the destruction of the Peragus Mining Facility, Lieutenant Grenn, upon their arrival on Citadel Station, restricted Meetra Surik and her companions, Atton Rand and Kreia, to the station while the Republic investigated the disaster. This followed a brief period of confinement in a TSF force cage and house arrest, pending preliminary examinations by the Telosian Council. While detained in the TSF station, an assassin, disguised as TSF officer Batu Rem, infiltrated the holding cell and attempted to assassinate the group. After the assassin's defeat, Grenn initially suspected Surik of attempting an escape. However, upon discovering the true identity of the disguised bounty hunter, he acknowledged the seriousness of the situation, assuring the group that such an infiltration was highly unusual and would not be repeated.
Later, Surik, aided by the Ithorian herd initially overseeing the Telosian Restoration Project, managed to leave for the surface of the planet unnoticed by Grenn and the TSF. She departed the station via an orbital shuttle in search of her starship, the Ebon Hawk, which had been stolen from a TSF impound dock.
Eventually, she returned to Citadel Station to meet with Grenn again, presenting an offer from Vogga the Hutt to supply fuel from Sleheyron to sustain the titanic space station in orbit and continue surface operations for the restoration project. Before her departure to the surface, Surik assisted Grenn in identifying the source of a modified holdout blaster, leading to the dismantling of a major smuggling operation on the station controlled by Samhan Dobo, and performing other work for him. This included locating dangerous criminals and securing the testimony and safety of Batono, a former Czerka Corporation employee with evidence of the corporation's illicit activities.
Unfortunately, Lieutenant Grenn and the TSF appeared to be largely ineffective. They were unable to prevent the theft of the Ebon Hawk, and TSF officer Batu Rem was kidnapped and replaced by an assassin from Nar Shaddaa, who infiltrated the station and the TSF in pursuit of the bounty on Surik. The TSF also struggled to contain the spread of the Exchange and control the mercenary population on Citadel Station. Furthermore, the TSF suffered from internal bureaucracy within the Telosian Council, a shortage of trained personnel, and insufficient funding. Despite these challenges, Grenn and his officers did their best with the resources available.
Later that year, Grenn was compelled to lead the military defense of Citadel Station during Darth Nihilus's attack on Telos IV. The Ravager and a fleet of Sith warships emerged from hyperspace above Telos without warning. With only a small force at his disposal, Grenn sent out distress calls. A force of Khoonda militia, led by Zherron, arrived, and Queen Talia dispatched soldiers from Onderon, commanded by the newly-promoted Major Riiken, to assist. Meetra Surik, who had recently arrived in pursuit of Darth Traya, offered her and her companions' assistance in the defense. She personally led the effort to secure the TSF Headquarters, preventing the sabotage of Citadel's fuel systems by Sith soldiers and Dark Jedi. With the situation on the station stabilized and Republic reinforcements, led by Admiral Carth Onasi aboard the Sojourn, arriving, Surik, along with Mandalore and Visas Marr, boarded a transport shuttle to the Ravager and destroyed the ship, forcing the Sith fleet to retreat. Upon returning to the station, Grenn delivered a message from Admiral Onasi to Surik, requesting a meeting to discuss a "mutual acquaintance," who was revealed to be Revan.
Dol Grenn was, in essence, a dedicated defender of the law. Despite his appearance as a hardened veteran enforcer adhering strictly to the government's policies and guidelines for rebuilding Telos, he was willing to act outside the established system to achieve results. This was evident in his willingness to accept assistance from Meetra Surik in resolving issues that the Telosian Security Force was unable to address. Grenn maintained that, as a soldier, he lacked the skills necessary for diplomatic duties, which he believed were essential to resolving the station's fuel shortage following the destruction of Peragus. Although direct in his speech, Grenn was true to his word and always rewarded successful efforts. He also held a cynical view of the Republic's overall state, which he freely expressed when appropriate.
Many of the tasks Grenn offers are optional, such as locating Batono and identifying the assassin who attempted to kill Meetra Surik and her companions. Additionally, players who choose the dark side path can undermine the TSF's efforts on Citadel Station by siding with Czerka in the Batono situation, either by killing him or handing him over to Jana Lorso. If the player continues down the dark side path, Grenn simply comments on Surik's appearance when she returns to Citadel Station to fight Nihilus' forces, asking if she has contracted a plague.