Vhaeraun

Vhaeraun was born as the son of Corellon Larethian and Lolth, as the elder twin brother of Eilistraee. About -30,000 DR, Lolth (at that time called Araushnee) tried to overthrow her husband as the head of the elven pantheon.
"You are still willing to do these things? After all, he is your father." Lolth to Vhaeraun, talking about their betrayal.
Vhaeraun was her confidant in this betrayal. He was unique in that he didn't feel attachment to membership in the Seldarine, suggesting the option of simply leaving the group, and he also didn't see inherent value in blood ties. What gave Araushnee the final nudge away from the Seldarine was a combination of realizing that she was alone, after understanding her son's capability to betray his father and his potential to murder her later to come out on top.
And he is your lord husband. If there is a difference, please explain it to me." Vhaeraun to Lolth, talking about their betrayal.
Eilistraee was intended to be the unknowing murderer of her father and the scapegoat for the betrayal. The plan involved Corellon's sheath, on which a curse was placed. Vhaeraun was the one who hid Corellon's sheath, so that Eilistraee would find it, which she did out of her known affection towards her father. The sheath was cursed to direct her arrows to the bearer, Corellon, and retrieving it and giving it back to him guaranteed that she would be in his vicinity when the battle ensued. Vhaeraun's other role was to imprison Sehanine Moonbow. She needed to be imprisoned because his mother Lolth conducted the very first step of the betrayal in plain sight of the moon goddess, thus revealing it to her. The moon goddess eventually managed to escape her prison, albeit at high cost to herself. During the war, Vhaeraun protected Araushnee. After the war, a trial was called, and Vhaeraun was one of those sent into exile from the Seldarine.

The Time of Dragons
Vhaeraun's influence spreads like a bloodstain upon the land. Finally, he became strong enough to achieve that which he most desired." Eilistraee on Vhaeraun.
During the Time of Dragons, the first elves came to Toril. They didn't know about the Seldarine and mostly strove to live in scattered tribes with one exception, the Ilythiiri. Among them, Vhaeraun became the mainstream deity in the first elven state Ilythiir.
He, and to a lesser degree Ghaunadaur, helped their people to carefully but successfully expand their territory throughout southern Faerûn (at that time the name for the single continent on Toril) and power, to a level that kept them independent from the dragons. Eilistraee tried to stop Vhaeraun's evil machinations,[168] for which he tried to kill her.
Throughout this time, he maintained thin ties with his mother.[169] Without any evil intentions, the moon elf Kethryllia Amarillis drew Lolth to Toril in -24,400 DR; the Spider Queen then made inroads in the southern state of Ilythiir.

The First Flowering
Vhaeraun became the most popular deity in southern Ilythiir, as that nation spread throughout the south of the continent, with Vhaeraun as the driving force behind this development. This position of hegemony changed with the First Sundering in -17,600 DR.
Despite vastly different views, Ilythiir was originally on good footing with the other elven nations, but Lolth poisoned the relationships between dark elves and other subraces. Seldarine-following elves came up with the idea to create a dark elf-free piece of land for those weary of the difficulties on the continent. They used elven high magic, and while they succeeded at creating their island, Evermeet, they damaged the continent, with accompanying casualties, among them many citizens of Ilythiir, as collateral damage. Among this collateral damage was a large part of the church of Vhaeraun. The Masked Lord's influence ebbed with the loss of his worshipers. According to Szorak Auzkovyn, Vhaeraun's salvage efforts were foiled by Eilistraee, through her favoring of female followers and excluding men from her clergy, thus causing a schism in the egalitarian church of Vhaeraun by seducing the women away to her. Lolth then became the hegemonic deity in Ilythiir, allowing her to start her machinations to corrupt and destroy all elves, which culminated in the Crown Wars.

The Crown Wars
Aryvandaar, a sun elf kingdom, had borderline genocidal intentions regarding the dark elves of Ilythiir at latest after the Dark Disaster. Geirildin Sethomiir, the coronal of Ilythiir, read even earlier those intentions in the actions of Aryvandaar. The coming battles were viewed and treated as battles for survival, so he made a pact with Lolth by proxy of Wendonai, around -11,500 DR, to gain the power needed to save his people. This act made Lolth the most important deity in Ilythiir.
Nobles of Ilythiir followed the example of their coronal and made their own pacts, and Vhaeraun, no longer the main deity, supported the dark elves of Ilythiir with servants and other support during the battles, alongside Ghaunadaur and Kiaransalee.
It is not very clear what kind of role Vhaeraun filled during the Crown Wars, though it was known that it was not one as a warmonger; that role fell to Lolth and Ghaunadaur.
The Ilythiiri, who were still refining their worship of the Dark Seldarine, used to portray their gods as spider deities, and high priests were killed by the offended gods for promoting this kind of iconography. Vhaeraun, for example, was depicted as a Masked Spider.
The Crown Wars destroyed most elven realms, including Ilythiir.[99] By the end of this era, Vhaeraun and Lolth were enemies.
Vhaeraun and Eilistraee joined Lolth in forming the new drow pantheon. Other deities joined them later.