Lethon

Lethon is one of the four Dragons of Nightmare. He was previously a world boss in the original Dragons of Nightmare event.

Dragons of Nightmare
In recent times, Ysera's most trusted lieutenants have been warped by a dark new power within the Emerald Dream known as the Emerald Nightmare. These wayward sentinels passed through the Great Trees into Azeroth, intending to spread madness and terror throughout the mortal kingdoms.

Lethon's exposure to the Nightmare not only darkened the hue of the mighty dragon's scales but also empowered him with the ability to extract malevolent shades from his enemies. Once joined with their master, the shades imbued the dragon with healing energies. It came as no surprise, then, that Lethon was considered to be among the most formidable of Ysera's wayward lieutenants. Lethon was in the end slain, however, this was not the last seen of him: Lethon's dreamform survived the defeat and thrived in the Emerald Dream.

Stormrage
During the War Against the Nightmare, Lethon attacked Ysera but she was able to defend herself. He was among the strongest of the Nightmare's servants and repeatedly helped to thwart the efforts of those fighting against it. Lethon attacked Tyrande, Broll, Eranikus, and Gnarl, When they were to enter into Emerald Nightmare. Gnarl tried to protect the night elves, only to be sucked into the Emerald Dream. Lethon then attacked Eranikus in order to corrupt him, but then Alexstrasza came and Lethon alongside Emeriss were forced to retreat.

After Ysera was captured and imprisoned within The Eye, Malfurion Stormrage and Ysera's consort Eranikus attempted to free her, but Lethon ambushed them and attempted to corrupt Eranikus. As Lethon preached about a future where the walls of the Nightmare would break down, and they would fly Azeroth's skies unimpeded, Eranikus shifted them both into the unstable boundary between the Emerald Dream and Azeroth. Though Lethon desperately tried to draw upon the Nightmare's power, the chaotic energies between the two worlds tore him apart.

Legion
When Ysondre is taken by the Emerald Nightmare once again, the corrupted spirits of her deceased comrades join her in the Emerald Dreamway, including Lethon. After the defeat of Xavius, Lethon's spirit along with the spirits of the other three former Dragons of Nightmare are seen in the restored Emerald Dream.

Stormrage

 * "Your greatest nightmare comes true..."
 * "Give in to the Nightmare! Let it embrace you!"