K'Varn

K'Varn the Mad was a mutated beholder and the major antagonist in Chapter 1. With a Horn of Orcus embedded in his forehead, K'Varn took control of denizens of the Underdark in preparation for an assault of the surface world. As an NPC, he was played by Matthew Mercer.

Background
K'Varn originally hailed from the Far Realm. At some point, he became aware of a Horn of Orcus and, over time, was able to pull the horn from the Material Plane into the Far Realm, where he merged with the evil artifact. He eventually made his way to the Material Plane.

K'Varn entered through a rift near the edge of the illithid city Yug'Voril. Either not knowing about the colony's existence or deciding that the risk was too great to try and control the mind flayers' elder brain, he made his way upwards.

He would later discover the duergar fortress of Emberhold. Using his power, he waged a battle with the duergar and won, enslaving them through fear and the promise of power.

Four months prior to Vox Machina entering the Underdark in search of Lady Kima, the duergar captured an illithid from the colony, which K'Varn most likely interrogated and either enslaved or killed. He then ordered the duergar army down to Yug'Voril where they attacked. Using this as a distraction, he infiltrated the elder brain temple and seized control of the hive mind, forcing the illithid to surrender.

With both the illithid and the duergar under his control, he started to make plans to assault the surface world. He began to enslave the creatures that lived in the tunnels near both colonies, and used his newfound power from the horn to twist and remake these creatures into aberrations for the upcoming war. He even mutated and modified his own body to strengthen himself.

He began to test the strength of the dwarven city of Kraghammer, using the mithral mine network below the city to send his new mutations through. While the dwarven military dealt with these abominations, he sent duergar to collect any dwarves caught inside the mines for slave labor and experimentation.

Vox Machina had also previously dealt with mutated abominations coming from deep underground. Whether or not these were K'Varn's creations is unknown.

Into the Underdark
Originally, Vox Machina was tasked by Lady Allura with finding and returning Lady Kima to Emon. After learning Kima had traveled to Kraghammer to stop a great evil from reaching the surface, the party traveled there. They quickly learned she had been driven down into the Greyspine Quarry by the Carvers, and after learning about more abominations coming up out of the ground and even fighting one while they were there, the party followed.

K'Varn was first mentioned to the party by a duergar that they had taken prisoner, which revealed to them that he was responsible for the modifications to the monsters that have been coming up to the surface.

Later, once Pike joined the group down in the Underdark, she mentioned that she'd had a vision of a very dark, unseen being deep beneath the surface.

After meeting Clarota, the party once again heard about K'Varn and how he had united the illithid and duergar into a single military force. They then allied with Clarota, not only to find Lady Kima, but also to kill K'Varn.

Once again, the group heard about K'Varn after capturing and interrogating a duergar general. It was here that the first mention of the Horn of Orcus came up.

While interrogating the duergar queen, K'Varn took control of her mind and "welcomed" Vox Machina to the Underdark, telling them that he would be waiting for them at the illithid city. He then psychically killed the duergar queen.

As the party rested in preparation to attack the elder brain temple in Yug'Voril, Keyleth discovered, while in spirit form, that K'Varn was a beholder that merged with one of the Horns of Orcus, and had also attached metal plating to his body. He had also erected a crystal-like structure above the elder brain to secure his control over the illithid city. She barely escaped when K'Varn psychically attacked her.

Temple Showdown
To enter the temple, the party dropped a fomorian on top of the crystal structure built into the roof of K'Varn's stronghold, freeing the illithid in the process. While in combat with the creature, Tiberius was too terrified to fight a beholder, and instead rushed out to enlist the illithid to join them in the fight. Lady Kima was turned to stone by one of K'Varn's eye rays while attempting to attack the beholder. Grog almost died from a series of K'Varn's eye rays, but Pike's Death Ward spell — cast directly before the battle — and an immediate Revivify managed to prevent the worst. Eventually, Vox Machina managed to kill K'Varn with a combination of repetitive damage, quick healing, and lucky saving throws.

Death
After K'Varn fell to Vex'ahlia's arrow, the party rejoiced until they noticed the Horn of Orcus bringing him back as a zombie beholder. This prodded Tiberius into action, and after a failed attempt and some additional damage, he succeeded in ripping the horn from K'Varn's forehead. This ended K'Varn's life, though the horn still holds all of its original power.

Aftermath
Because K'Varn was the unifying force in the illithid/duergar alliance, it is presumed that the united army is no more and that both groups have returned to their respective cities.

The duergar city of Emberhold was badly damaged during Vox Machina's assault, and their king and queen were killed as well. It is unlikely that the duergar will pose any threat to the surface.

The illithid's elder brain was badly hurt by Vox Machina after Clarota and the illithid betrayed them and the party was forced to flee for their lives. The illithid also still possess many of K'Varn's twisted creations, and could probably control them using their psychic abilities, turning them into weapons. It is unclear if the illithid will retaliate against the surface, though several of the council members of Emon don't seem to think they are a threat. Clarota also stated before the events at the duergar war camp that his people had no interest in the surface world.

Vox Machina obtained the Horn of Orcus from K'Varn's body. They later sealed it in a vault far beneath the Platinum Sanctuary in Vasselheim, with the consent of the Council of Emon.

Personality
K'Varn was a twisted and evil creature, and the horn most likely strengthened these traits within him. He clearly believed himself to be all-powerful and indestructible. However, he was very intelligent, and one of the most dangerous creatures Vox Machina has ever fought.

Whether or not he was under Orcus's direction or his own is not entirely clear.

Artifacts

 * Horn of Orcus

Abilities
Due to the horn's influence, it is unknown how strong K'Varn was before obtaining the evil artifact. Since he was a beholder, though, he was most likely already incredibly powerful prior to obtaining the horn. He could cast at least one spell out of each of his eyes.

Beholder Abilities

 * Anti-Magic Eye Cone
 * Eye of Anger
 * Eye of Death
 * Eye of Disintegration
 * Eye of Health Absorption
 * Eye of Petrification
 * Eye of Soul Absorption
 * Eye of Telekinesis
 * Mind Control
 * Mind Reading

Mutated Abilities

 * Greater health
 * Armor plating

Horn of Orcus Abilities

 * Enhanced power
 * Undead resurrection (most likely power of Orcus instead of K'Varn himself)