Ahem, might as well explain this au

Around the time Goggles was created he was made to become a goddess of power. however, the goddess that created him was a rival with another goddess. The rival goddess created Rider. The rival cursed Goggles to be killed by a close friend (same happened to Rider). Much to the goddesses surprise, Goggles and Rider became close friends. A few years after Goggles fought against Vintage, Rider was forced to kill Goggles despite not wanting to.

Right after Goggles died he appeared in a void of nothing with a dragon. The Dragon of Curses. The dragon asked Goggles if he would rather go to Heaven or Hell since Goggles curse was fulfilled. The dragon told him that if he went to Hell he would have freedom in exchange for never seeing his friends again and becoming a Dragonbound of Curses taking the dragons place. Or go to Heaven where he would be forced to spend over a million years alone to become the new goddess of power and having his friends forget him. He would have no freedom up there.

Goggles eventually decied to go to Hell seeing how he wouldn't be alone for the rest of his life. The dragon nodded and disappeared. Goggles became a Dragonbound. He was now the Dragonbound of Curses.

To be a dragon of curses you had one job. If someone who was cursed died they'd be sent to you. And you decided if they should be sent to Hell to finish off the curse or send them to Heaven if they fulfilled it. That was Goggles job now.

He did become friends with the sacred king of Hell, Paimon. Paimon was a close friend of the dragon so helped Goggles to make right decisions.

Goggles eventually found out Rider killed him. Why he doesn't know. But he wanted revenge. Whatever friendship he has with Rider seemed to go into the void never to be seen again. He wanted to make him pay.