When Orphen was adapted in the 90s the original novels didn't had a conventional villain at the time so they just ripped off Rezo and called it a day, Flameheart follows all the steps they would take with Rezo in the Slayers anime
>Pretends to be nice, has many followers, is respected, but is hiding his true intentions
>*Dies*
>Seemingly comes back, but it turns out not to be the real one
>Comes back a third time but now he's possessing the body of another character which ends up being destroyed
>*Permadies then the show ends*
Keep in mind that the last step was long before Slayers Evolution-R, so Slayers copied the copy in that one, it was the same studio after all, and Flameheart had the exact same voice and VA as Rezo