Well of Eternity

The Well of Eternity is a magical pool of water in the Warcraft Universe, and is a source of arcane magic.

Centuries ago, the Night Elves dabbled in the use of arcane magics. Many of the Highborne became addicted to their use and refused to give such up, even with the coming of the Burning Legion. Their refusal sparked a civil war between the two main factions of Night Elves: those who sought to use the magic for its power, and those who felt that it should be forbidden, lest the Burning Legion return in force once more. In the end, the Well of Eternity was destroyed, and the resulting magical shockwave sent the Highborne to the bottom of the sea.

The remaining Night Elves considered that the end of the matter, trusting that with the destruction of the well, the Burning Legion had no further cause to invade. However, Illidan Stormrage, who had fought valiantly as a demon hunter during the war against the Burning Legion, a bold survivor of the well's destruction was addicted to magic and had no intention of foregoing it's use. In the dark of the night he stole some a drop of water from the remnants of the well and used it to form a new body of water, thereby creating a new Well of Eternity. For this action, seen as traitorous and rash, he was imprisoned by his brother, Malfurion Stormrage, and placed under guard by the Warden Maiev Shadowsong.