As one of the Dominion's Vorta, Weyoun was the very essence of his cloned species, the trusted administrators bred by the Founders to handle day-to-day affairs and oversee the Jem'Hadar military. Weyoun was cloned a total of eight times.
Weyoun 4 was the Vorta field supervisor in 2372 during a joint Federation/Dominion mission in the Gamma Quadrant to destroy a powerful Iconian "gateway" in the possession of renegade Jem'Hadar soldiers. After the mission succeeded, Weyoun 4 was killed by his own Jem'Hadar First for questioning his troops' loyalty.
Weyoun 5 rose to a more significant position in the Dominion, that of chief liaison to the Cardassian government and field supervisor for all Alpha Quadrant operations. This clone was instrumental in the Dominion's military posturing in the Alpha Quadrant, and was a very close aide to the so-called "Female Shapeshifter" who primarily called the shots. He visited Deep Space 9 on several occasions starting in 2373, and even used it as his base of operations during the Dominion/Cardassian occupation of the station in 2373-2374. After evacuating DS9, Weyoun 5 oversaw the transition of Cardassian leadership from Gul Dukat to Legate Damar. The fifth Weyoun lived less than two years, dying in 2375 in a transporter "accident." (Foul play was suspected, but a thorough investigation found no evidence.)
A month after being activated, Weyoun 6 defected from the Dominion in a crisis of conscience over the war. He put his fate into the hands of Odo, who attempted to bring him to Deep Space 9 while under pursuit by Jem'Hadar forces. In order to ensure Odo's safety, though, Weyoun 6 terminated himself by triggering an implant in his brain (one that all Vorta have).
Although normally a new clone is activated only upon the death of the old one, Weyoun 7 was created when his "defective" predecessor fled, and guided the effort to hunt him down. The seventh incarnation served in Weyoun's normal capacity for several months, until he provoked Worf into snapping his neck.
Weyoun 8 was quickly put into service with hardly any interruption of routine. This Vorta faced the betrayal of Damar and the rise of his Cardassian resistance force. In fact, Damar's first act of subversion was to destroy the cloning facilities on Rondac 3, ensuring that number 8 would be the last Weyoun. Weyoun 8 served the Female Shapeshifter faithfully — even fulfilling the uncomfortable command to order the extinction of the Cardassian race — until he died at the hands of a Cardassian, Garak, when resistance forces infiltrated Dominion headquarters.