Zaggar

Zaggar is the het ship between Zarkon and Haggar from the Voltron: Legendary Defender fandom.

Canon
Over 10,000 years ago, before the events of the series, a trans-reality comet crashed into Zarkon's home planet, Daibazaal. His allies from planet Altea came to investigate, including an Altean alchemist named Honerva. As Honerva studied the rift left by the comet, Zarkon fell in love with her and married her. Honerva and Zarkon soon became obsessed with quintessence, unfathomable energy found inside the rift, at the expense of the planet's stability and Honerva's health. Before Honerva became to loss her sanity and her health began to waver, she became pregnant with their son which exists the both of them as they would wait to be parents, the new also encouraged them to continue their quintessence gathering from the rift, for their son's empire. As they discus the name that Zarkon and Honerva wanted to give their son, since they were both thinking about names from their separate cultures, Honerva helps to settle the matter by merging their Altean-Galra name choices together to make it fair.

In order to save his wife and their unborn child, Zarkon tricked his allies into using Voltron to expand the rift, making them believe it must be done first in order to close it; he exited Voltron and entered the rift with the deathly ill Honerva, attempting to heal her with quintessence, but both were overcome by dark creatures from another reality. The ordeal left them both presumably dead and a funeral was held. However, Zarkon suddenly reawakened, changed and corrupted into an evil being, as did Honerva. Who had forgotten who she is, while Zarkon's corrupted state has him allowing her to become Haggar, a witch serving as the high priestess of a group of Druids that support Zarkon's evil Galra Empire. In order to gain more quintessence through the use of their dark magic. As the long years pasted, Zarkon's love for his wife was replaced with a desire for power, while Haggar serves as his fateful witch. Haggar does not regain her memories until prying into the mind of Zarkon when he is comatose, in an attempt to revive him.

Even though Haggar's memories as Honerva were returned to her, she choice their son Lotor over Zarkon when she learned the danger that he'll place their son in. After Honerva learned that her son is also gone, her desire to have her family back, along with the life she and Zarkon could of had with Lotor, she recruited the Alteans Lotor had rescued and hide from Zarkon, in order to set the stages of her plan that would allow her to find a perfect alternate reality that would allow her to be with Zarkon again. When the Paladins went into Honerva's mind to find out what she is planning, they come across Zarkon's spirit who served as one of Honerva's guardians to protect her thoughts and memories from intruders, once they freed Paladin Zarkon from her hold, as well as the evil that corrupted both of them, he helps them find the answers they seek in order to repent for the suffering he and Haggar had caused. Zarkon's help allowed him to see Honerva's cherished memories of the two of them together, before the maddens they started began, allow with the times she wishes for them to share with a child Lotor.

When Honerva found the alternate reality she seeks, where her alternate counterpart of that reality had passed away, she treated its version of Zarkon like he is really her Zarkon who is happy to have his wife back in his life. Just when she was being to have the happy life she seeks with her "replacement" Zarkon, the alternate reality's version of child Lotor didn't except her and has Zarkon tried to reason with her about giving Lotor time to except the woman who calls herself their Honerva, she became enraged that despite all that she had done to be with her husband again. The moment Voltron caught up to her, Zarkon mistook Voltron for a threat that Honerva brought with her and realized that his son is right about her not being his wife. Believing that she'll never be happy with Zarkon again, Honerva destroys the other realities to destroy the universe itself, but Allura and the rest of the Paladins mange to stope and reason with Honerva about what she is doing. With Allura's help, as they give up their lives to restore the damage she had caused, Honerva is finally reunited herself with her Zarkon and Lotor who except her. Which grants the happiness she longed to have with Zarkon again.

Children
Prince Lotor Lotor was conceived 10,000 years ago, before Honerva entered the rift; he has stated that Honerva is his mother and that Zarkon is his father. While he is aware that Haggar used to be Honerva, he believes that the one he could call his mother died all those years ago. He is disdainful of both Zarkon and Haggar, but has seemed proud of Honerva's experiments on Daibazaal's trans-reality rift.

Fanon
Fans suspected that there was something between Zarkon and Haggar at the end of season 2, when Haggar seemed more worried about Zarkon's self-destructive habits than anyone else. When the couple was confirmed canon, fans then went on to try and draw parallels between Zaggar and their own favorite ships, mostly Sheith.

Fandom
FAN FICTION
 * Zarkon/Haggar on FanFiction.Net

AO3

Trivia

 * From the canon material, some fans notice similarities of the ship to Sheith, due to Keith and Shiro's strong connection to each other.