The Convocation of Silvermoon (also known as the Council of Silvermoon) was the ruling power over Quel'Thalas. Despite that, the Sunstriders maintained a modicum of political power as the royal house.
The Guardians of Tirisfal
Over 3,000 years ago the Magocrats of Dalaran contacted the Council as demons started to appear in the streets of the magical city-state. After dispatching their mightiest wizards to the human lands to investigate, the Convocation's agents concluded that there were only a few demons loose in the world; although, the Legion itself would remain a dire threat so long as humans continued to wield the forces of magic.
The elven lords entered into a secret pact with the Magocrat lords, revealing them the history of ancient Kalimdor and the Burning Legion. Both groups decided to found an order that would fight a never-ending secret war against the invaders from the Nether.
The king and the Convocation convened to discuss the matter of the Old Horde's invasion of Azeroth during the Second War. Given how far the invaders were from Quel'Thalas, they were hesitant to dedicate themselves to the conflict, believing the orcs sought only to conquer human lands. Regardless, the presence of Anduin Lothar (last of the Arathi bloodline) required homage from King Anasterian for the Troll Wars millennia before, and the king and the council authorized a token force to be sent to Hillsbrad.
Alleria Windrunner confronted the council after returning from the south, hoping to convince them to mobilize the elves' full might. She met opposition from the Convocation, who claimed that the presence of Amani in the Horde's ranks meant the orcs may even lead the trolls away from Quel'Thalas, and that even if an invasion was to occur, the invaders would never be able to overcome the runestones. However, Alleria reported that the Amani had already mobilized and started attacking the elves, which provoked an angered reaction from Anasterian. The king ordered the high elf armies to be rallied and the Amani to be wiped out for good.
Most of the Convocation remained on Quel'Danas during the Scourge invasion of Quel'Thalas. When Ban'dinoriel (the great shield protecting Silvermoon City) was dispelled, Convocation member Grand Magister Belo'vir, who was commanding Silvermoon's defense, immediately ordered the council to raise a barrier in its place, though word did not reach them in time: roughly half of the council had been individually murdered near the Sunwell Plateau by the treacherous Dar'Khan Drathir (who had long envied and despised the Convocation for their high place and, as he saw it, their refusal to share the power of the Sunwell), though the traitor noticed Belo'vir's absence. By murdering key members of the council who had the knowledge to stop him, Dar'Khan was able to hide what he had planned for the Sunwell, and bound its energies.
The rest of the Convocation, bent on unraveling the mystery of the bound Sunwell, remained at the plateau while Belo'vir led an army of magi, priests, archers and rangers to combat the Scourge. The battle ended in disaster for the elves: King Anasterian, along with Belo'vir and a staggering 90% of their people, all fell to the Scourge's might. The surviving Convocation members were eventually driven away and wiped out by the Scourge, who proceeded to corrupt the Sunwell and raze the isle.
The council ceased to rule over the kingdom after its devastation at the hands of the Scourge, as the Sunstrider heir went on to become the sole leader of the Thalassian people; from then on, they would be known as the blood elves.
An early Archaeology article stated that an "unknown council" based in Silvermoon was behind the recent revitalization of the Reliquary. No information has been given since, but it has been speculated that this may be a sort of reincarnation of the Convocation.