Haggar (formerly known as Empress Honerva) is the central antagonist of Voltron: Legendary Defender. She is the secondary antagonist of the first four seasons and essentially the main antagonist in Season 8. Due to posing a threat to all reality, she is arguably the overall main antagonist of Voltron: Legendary Defender.
Having lived for over 10,000 years, she is a powerful sorceress, who serves as the advisor to Emperor Zarkon and leads the Druids of the Galra Empire, until Zarkon's death at the hands of her own son. Years after, she became more malevolent and more powerful than ever, and engineered a plot to destroy all reality, by destroying the Realm Of Existence. She was finally defeated at the hands at Voltron, thus saving the realities altogether.
Ten Thousand Years Prior
Honerva was one of the best alchemists on Altea, and came, on the request of King Alfor, to the Galra home planet Daibaazal to investigate the rift that was left by the dimensional reality comet that crashed onto the planet. It was here that she met Daibaazal's king, Zarkon, who became smitten with her.
For many years, Honerva would remain on Daibaazal investigating the rift and marry Zarkon during that time.
One day, Alfor comes to check up on her research, and when asked about the dark creature, Honerva explained that she sent signals into the other reality and the creature answered. Alfor reminds her that she was supposed to exercise caution on acts like this, but Honerva insists that they must keep pushing the boundaries in the pursuit of knowledge. When the dark creature summons more of its kind through the rift, she and Alfor were able to contain them in a particle barrier, but it won't be able to hold the creatures for long. The dark creatures were soon defeated by Alfor's creation, Voltron, but despite Alfor's insistance on sealing the rift, Zarkon keeps it opened, and Honerva continued her experiments with the rift.
Some time has passed when Alfor visits again, and finds that Honerva used Quintessence from the rift on her cat, Kova, when he became ill which lengthened his normal lifespan. Not only that, but the prolong exposure to Quintessence has taken a toll on Honerva mental and physical health, to the point that she ends up fainting after Alfor leaves.
Fatally ill and losing her mind, Honerva rambles about going into the rift using Voltron, and Zarkon tricks Alfor and the other Voltron Paladins into doing just that. Inside the rift, Zarkon exposes Honerva to pure Quintessence when they are then swarmed by the dark creatures that attacked Daibazaal. Voltron is able to rescue Zarkon and Honerva, only to find that they have both died from overexposure. As the further opening of the rift had further destabilized Daibazaal, Alfor evacuated the planet destroyed it in order to close the rift forever. After being held a funeral, the two are revealed to be alive and corrupted by the Quintessence, with Honerva losing all of her memories and becoming Haggar.
Haggar is a cruel and insane sorceress who cares for no one but Zarkon and harvesting all of the Quintessence in the galaxy. This cruelty is especially shown in her experimentation and torturing of prisoners. Her thousand years of experience and high intellect make her highly confident in dealing with anyone until she inadvertantly unlocked Allura's magical abilities and the Altean princess uses it against Haggar does the witch become terrified to the point of retreating. Though she loses her memory of being Zarkon's wife, the love that her previous life as Honerva has for him shows through in Haggar as she faithfully serves Zarkon and worries about his unhealthy obsession with recapturing Voltron. This also extends to preserving his rule over the empire as she summoned Lotor to rule as Emperor Pro Tem to hold the empire together. Though she would later revive Zarkon when Lotor was not performing his job.
In contrast to Zarkon who reduced into irredeemable malevolent tyrant who remained evil to the end, Haggar still retain traces of her old self Honerva. However, it all rendered dormant by very corruption that change her physically and mentally until they resurfaced when she caught vision of her past life as she attempted to revive comatose Zarkon. Wary at first, she began to understood the recollection the more she use quintessence, allowing her old self Honerva to slowly resurface for the first time in thousands of years but keep the truth about her past and change a secret from everyone. This become apparent upon receiving more visions via. quintessence which revealed that Lotor is her and Zarkon's son, something which made Haggar shocked and devastated (as the said visions also revealed that baby Lotor was lonely due to what his parents had become). These ultimately shattered her loyalty to her now-monstrous husband where she plotted against him to ensure his defeat, Lotor's survival, and her son's ascension to the throne with Sendak and Shiro.