WARNING: The following article contains spoilers for Season 3 of Netflix's The Dragon Prince, streaming now.
The first season of Netflix's The Dragon Prince deliberately left ambiguous the fate of the Dragon King. We knew he died, but the specifics remained hidden and left to the viewer to imagine how the behemoth fell, leaving behind his son, Zym, who hatched in Katolis. However, at long last, Season 3 fills in this major plot hole by showing us it wasn't actually Viren's legion as initially assumed. The killer was, shockingly, King Harrow, Ezran's dad, and his vindictive behavior resulted in Zym coming to Katolis and the start of a new magical war between bloodthirsty humans and the realm of Xadia.
THE MYSTICAL SPEAR
With Viren freed thanks to Aaravos corrupting the human alliance, Ezran is put in prison in his place. Viren then takes the alliance to destroy the magical Xadia under Aaravos' watch, so they can kill off all the remaining elves and dragons. While on the journey, Aaravos asks about the king, Thunder, and how he fell. The evil elf hated the king just as much as Viren, as it's hinted Thunder helped seal Aaravos away in his magic mirror in Season 1.
Viren regales his colleague with the story, revealing after Thunder killed Harrow's wife in battle, he tricked the king into revenge. In a flashback, we discover Harrow did let his hatred die down, but Viren used a dead unicorn and harnessed its magic to create a dragon-killing spear. All he needed was Harrow's rage and the weapon would be complete. Once this was done, Harrow actually became angry again and wanted Thunder dead.
THE FALL OF KING THUNDER
The duo rode out to Xadia, but Thunder made it clear he didn't have time for bloodshed on that day, clearly trying to get back to the Storm Spire mountain to protect something valuable. Nonetheless, Harrow provoked him into a fight and when Viren used his dark magic to restrain the beast, the king tossed the spear into the heart of the Dragon King.
It was a painful death, as Thunder turned to stone, crying out in pain as he looked to the Spire. The manipulated Harrow wanted to leave, feeling guilty, knowing this isn't what his queen would have wanted, but Viren, with his permission, headed to the mountaintop to see what was being stored. There, he discovered the egg containing Zym and enraged by the prospect of more dragons being born, Viren set out to destroy it.
PROJECT ZYM
With the Dragon Queen out on a foraging mission, the only hurdles in Viren's path are two elves, Rayla's parents, who seemingly deserted Xadia in Season 1. It turns out they didn't flee with the deserters, they decided to stay to protect the egg in the queen's absence, even though Thunder had fallen. The other elves feared the killers, but Rayla's parents didn't and felt it was their duty to ensure the egg's safety.
However, Viren used his magic to freeze them before he approached the egg to crush it. Rayla's mother, in a last resort, urged him not to kill the baby, but to wait until it hatched to harness the magic the beast held within. This would make Viren a stronger dark mage and while it seemed a cruel sell-out, it was the only way to keep an unborn Zym alive. Rayla's parents hoped someone would someday free the creature, as Ezran did years later, but with the secret now unveiled, Viren killed the elves. He then made off in secret with the egg, thus kickstarting the events of Season 1, not knowing Ezran and Callum would discover and save the young dragon prince.
Netflix's The Dragon Prince Season 3 stars the voices of Jack DeSena as Callum, Sasha Rojen as Ezran, Paula Burrows as Rayla, Jesse Inocalla as Soren, Racquel Belmonte as Claudia, Luc Roderique as King Harrow of Katolis and Jason Simpson as Viren.