K'Varn

K'Varn is a mutated beholder, and is the major antagonist in Season One of the web series Critical Role. He is portrayed by Matthew Mercer.

Background
K'Varn originally hailed from the Ethereal plane. At some point he came across an artifact known as the Horn of Orcus, which enhanced his powers. He eventually made his way to the Material Plane.

K'Varn entered through a rift near the edge of an Illithid colony. Either not knowing about the colonies existence or deciding that the risk was too great to try and control the Elderbrain, he made his way upwards.

He would later discover the Duergar stronghold 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 for 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 the Illithid hive where they attacked. Using this as a distraction, he infiltrated the Elderbrain Temple and seized control of the hive mind, forcing the Illithid to surrender.

With Illithid and Duergar under his control, he began 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. Whether or not he was under Orcus's direction or his own is not entirely clear.

He began to test the strength of the Dwarven city of Kraghammer, using the mithril 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 Mochina was tasked with finding and returning Lady Kima to Emon by Lady Allura. 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.

After meeting Clarota, the party once again heard about K'Varn and how had united the Illithid and Duergar into a unified military force. They then made a pact with Clarota to not only find Lady Kima, but to also kill K'Varn.

While interrogating the Duergar queen, K'Varn possesses her mind and "welcomes" Vox Mochina to the Underdark, telling them that he will be waiting for them at the Illithid city. He then psychically kills the Duergar queen.

As the party rests up in preparation to attack the Illithid city, Keyleth discovers while in spirit form that K'Varn is a massive beholder that has merged with a Horn of Orcus and also attached metal plating to his body. He has also erected a crystal-like structure above the Elderbrain of the Illithid colony that keeps it under his control. She barely escapes as K'Varn tries to kill her.

Temple Showdown
In order to defeat the beholder, the party drops a Fomorian giant on top of the crystal structure to break into the roof of K'Varn's stronghold and free the Illithid in the process. While in combat with the creature, Tiberius is too terrified to fight a beholder, and instead tries to get the Illithid to join them in the fight. Grog is knocked unconscious and almost killed by the Illithid, however Pike is able to save him before he dies. Eventually, Vox Machina manages to kill K'Varn with a combination of repetitive damage, quick healing, and lucky saving throws.

Death
After K'Varn falls to Vex's Hail of Thorns, the party rejoices until they notice that the Horn of Orcus is bringing him back as an undead. This prods Tiberius into action, and after a failed attempt and some additional damage, he succeeds in ripping the horn from K'Varn's forehead. This ends K'Varn's life, and all of its magic, though the horn still holds power.

Artifacts

 * Horn of Orcus

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 Elderbrain was badly hurt by Vox Machina after Clarota and the Illithid betrayed them and they were forced to flee for their lives. It can possibly heal over time. The Illithid also still possess many of K'Varn's twisted creations, and could probably control them using their psychic abilities to turn 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.