The Komar is a massive machine that took Haggar and her Druids years to complete. It is a formidable and horrifying weapon that is capable of consuming the quintessence of an entire planet, leaving only death and destruction behind. This eliminates the Galra Empire's need to mine and colonize planets.
In "The Black Paladin," Haggar used the Komar's energy to corrupt the wormhole that the Castle of Lions managed to escape through, which resulted in scattering the team all over the galaxy.
It appears again in "Blackout," where Haggar turns its witchcraft against Voltron. Since its robot form is made of pure quintessence, the Komar only rendered it temporarily lifeless, and nearly wiped out Haggar. She continues to use the machine to attack and fight Voltron alongside Zarkon in his giant robot armor, until Allura destroyed it with her newfound magical abilities.
In "Lions' Pride, Part 2," after the enemy machine saps Voltron of its quintessence for the first time, both Pidge and Allura note that the attack felt like the Komar.