The High Gul was a Cardassian male who lived during the 23rd and 24th centuries. As leader of the Crescent Order, the High Gul was held in very high regard by Cardassians, akin to how George Washington and Christopher Columbus were seen by Humanity.
During a military campaign, the High Gul and 3,000 of his best men were put into stasis, with the intent that they would be awakened at an opportune time to bring the Cardassian people to victory. However a young man named Fransu stole the body of the High Gul and several of his closest soldiers, and killed the remainder of the troops. Fransu hid the bodies for many years, eventually burying the bodies in a vacuum sealed compartment on Terok Nor as the station was under construction. Over time, the tunnel leading up to the compartment became filled with debris and partially collapsed.
In the year 2371, Constable Odo and Chief Miles O'Brien were in the process of exploring the tunnel on Deep Space 9, as Terok Nor was called after the Cardassian withdrawal, when they came across the vacuum sealed compartment. Breaking into the compartment, they discovered the Cardassian bodies. When Elim Garak was brought in to advise the senior staff on how to handle the situation, he immediately recognized the High Gul, and returned later to the compartment in order to revive him and his aides.
Once awake, the High Gul and his aides attempted to take control of Deep Space 9. At the same time Fransu, by now a Gul himself, realized that the High Gul was awake, and proceeded to attack Deep Space 9 in an attempt to kill him.
After Captain Benjamin Sisko and the High Gul joined forces to defeat Fransu, the High Gul realized that his time had passed, and that his return to Cardassia would be disastrous to the Cardassian people. He then committed suicide with a hand phaser. (DS9 novel: Station Rage)