Why did Sepulchure put up with Chuckles' laughter? Simple — Chuckles was Gravelyn's first undead minion. "Daddy was so proud!"
Also, why is Artix so afraid of a Fear Feeder even though everyone knows he's afraid of pink? Look at the name of the monster; it feeds on fears! It'll feed on Artix's fear and grow so powerful that not even he, the undead slayer that he is, won't be strong enough to kill it.
Also, why is Artix undead in the Battleoff universe? This is because this is him if he gave into his destiny and became the Champion of Darkness instead of the Undead Slayer we know him to be.
After Drakath kills Sepulchure and leaves King Alteon chaorrupted, he parts with one last remark about how he'll leave Alteon and the Hero for last after destroying everything they love. Turns out, he had revealed who the last two Chaos Lords would be from the very start as King Alteon and then the Hero him/herself become the 12th and 13th Lords of Chaos respectively. This makes the scene Harsher in Hindsight as it shows that from the start, Drakath had planned to Chaorrupt the two for his purposes, proven by the Chaos Lords Boss Rush before the final battle with Drakath where it reveals that the past incarnations of the Chaos Lords were the 13 Heroes who sealed away the Queen of All Monsters into the Chaos Realm.