Breaching the Stygian Veil

Overview
Summary Obtained from
 * 1) Defeat the approaching demon hordes.
 * 2) Destroy the Demon Underlords to release the magical bindings placed on the entrance to the spawning tunnels. X of 2 Demon Underlords remain.
 * Adept of Whispers at Stygian Veil

Reward
 * 10,000 XP

Dialogue
 * [Difficulty: Master] "If we are to defeat the Dreadspawn Maw, we must fight our way through her children. Some will be fully-formed demons, but many of her spawn will only be half-formed and not yet have their full strength. One thing you can be certain of...her demonic forces will be near boundless. Will you help me fight past the demonic hordes?"
 * Accept: "Sure. How hard can a near infinite number of demons be?"
 * Decline: "I...uh...just remembered.... I have a thing at that place."
 * When asked about quest:
 * "We must destroy the demonic forces guarding the Stygian Veil"

Reward Dialog
 * ''"Now that we have weakened the Dreadspawn Maw's demonic forces, we must proceed into the spawning tunnels and destroy the Stygian Lords. Speak to me again when your ready."

Followup
 * Brood Wars