Dread Emperor

The Dread Emperor was one of the major enemies that Vox Machina fought prior to the stream. He was a deviation of the standard Dread Emperor from Dungeons & Dragons. As an NPC, he was played by Matthew Mercer.

Background
The Dread Emperor was a being that lived on a large island, which held a giant gothic castle surrounded by a bramble forest, floating through either the Astral Plane or a pocket dimension. In the Material Plane, the Dread Emperor used magic to appear as a child with black hair and golden eyes, but in his true form, he was a grown man wearing gold armor. The Dread Emperor abducted children, chaining them by the neck to his armor, gaining power from them. When the children became too old, he would kill them and put their bodies in the castle basement.

Before the Stream
Vox Machina was tasked with investigating the disappearances of various children throughout Tal'Dorei. Hearing about a suspicious child that would appear a week before each disappearance, the party kept their eyes peeled. Eventually, while celebrating their efforts for saving the city of Emon, they noticed the child talking to Sovereign Uriel Tal'Dorei's son. They attempted to capture the black-haired, golden-eyed boy, but he kidnapped the sovereign's son before Vox Machina could intervene. However, the party managed to find a way into the Dread Emperor's realm.

Approaching the bramble forest that surrounded the Dread Emperor's manor, a corrupted treant stepped forth from the vines toward Vox Machina. Using one of her druid spells (likely Command Plants, since it was Pathfinder), Keyleth convinced the corrupted treant to go back to sleep, averting a combat encounter.

During the final encounter in the Dread Emperor's library, Vox Machina realized that damage to him was magically suffered by the children chained to him. In order to defeat him without harming the children, the party tried to free them from him. They were able to save three of four children, as the last child was accidentally killed by Keyleth when she got into a tug-of-war with the Dread Emperor and the pressure on the child's collar broke his/her neck. Despite this casualty, they were able to defeat the Dread Emperor.

Aftermath
Vox Machina was able to return a majority of the abducted children to the Material Plane, where they were reunited with their families.

The incident regarding the child's death, however, weighed heavily on Keyleth's conscience, and it was interfering with her desire to do what was necessary to survive in addition to her training with the Earth Ashari during her time away from Vox Machina, as she revealed during the party's time at Pyrah. It became a sensitive subject for her, as shown the day after Vox Machina's first battle with the Briarwoods when Vax'ildan brought up the child's death in comparison to Tiberius's killing of an old woman. Keyleth quickly grew cold to Vax as a result, not even wanting to speak to him for a time. She eventually got over it while en route to Whitestone, but the memory of that day continued to haunt her.

Vox Machina briefly reunited with one such child, Simon Brist, and his mother, Elowen Brist, when encountering a camp of refugees from Westruun after the Chroma Conclave's attacks.

After Pike severed Craven Edge's connection to Grog with a Greater Restoration, Keyleth banished the evil sword the Dread Emperor's realm using Plane Shift. Due to the conflicting statements about the Dread Emperor's realm, it is unclear if Craven Edge is now in the Astral Plane, in a pocket dimension, or somewhere else altogether.

Personality
Little is known about the Dread Emperor other than he enjoyed being around children because of their innocence and naïveté. However, when his own life was at stake, he was willing to use those same children as a means of defense, even at the cost of their lives. He also killed the children that got too old, all of this suggesting a very amoral personality.

Abilities
The Dread Emperor's abilities are unknown, although it is clear that he possessed great power.
 * Polymorph
 * Unspecified interplanar transportation