A Quo'thalas in his suit
A Quo'thalas outside his suit, showing similarities with the Cyrollans on the right.
The Quo'thalas are an alien race somehow related to the Cyrollans, however this was not apparent as individuals appeared mostly enclosed in pods or suits. They were considered aggressive, violent and hostile by other races.
When their race was young, the elder Sosiqui had already past with only legends of their Legacy, a relic containing their vast knowledge. These legends led them to Earth where they met the Cyrollans. Peace failed and both fought for the Legacy. When one of the Qou'Thalas ships landed near the temple of Atlantis, the Cyrollans were forced to destroy the city, believing that this action saved the universe.
Cyrollans fighting Quo'thalas above El Dorado
The war continued for centuries. The Legacy resurfaced as two highly-advanced cultures and each time the cities was destroyed in brutal battle. After El Dorado and Sangri-La, the Cyrollans managed to chase the enemies into the outer regions of space.
In 2329 the Quo'thalas returned to Symbiotry space once more, making way for Earth, demanding to hand over the Legacy. Their aggressive appearance warned the Symbiotry. The TSA decided to send Agent Gage Blackwood to retrieve the Legacy from the past in order to fend off the menace.
The Cyrollans were then on hand to defend the Earth against the Quo'thalas attack, even going so far as to teleport into TSA headquarters to fight off Quo'thalas intruders. As Blackwood shouted that the Legacy belongs to "all races", a delegation of armed Cyrollans materialise at the other side of the lab.
Blacwood intervened saying that if both races fight over the Legacy once more the cycle of the past will continue. The Legacy fended off representatives of both races who approached it. It accepted only Blackwood who revealed that the Legacy's combined knowledge will be passed on to the many races of the galaxy only when they are mature enough. The two alien races agreed to abide by the Sosiqui's spirit's words and a peace agreement was finally made between the Quo'thalas and the Symbiotry.
After this, Gage Blackwood became ambassador to the Quo'thalas