An ancient Klingon emperor remembered for conquering the city of Tong Vey and ordering it burned and its people killed, a battle Worf replays in a holosuite before the Klingon transport incident.
Sompek was an emperor of the Klingon Empire in the distant past. His most famous victory was the Battle of Tong Vey, in which he led ten thousand warriors against the city and, once it had fallen, commanded that it be burned to the ground and its inhabitants put to death.
He is discussed in the Deep Space Nine episode Rules of Engagement. During Worf's extradition hearing the Klingon advocate Ch'Pok reveals that Worf ran a holosuite recreation of Tong Vey the day before the Defiant fired on what appeared to be a civilian transport, taking the role of Sompek and giving the order to destroy the city. Ch'Pok uses the programme to argue that Worf went into battle longing for slaughter.
Sompek is never shown; the programme is described in testimony only.