Two out of the six elders were traitors. They schemed and poisoned the two Supreme Elders, intending to kill all the inhabitants of the Walpurgis Night and destroy it once and for all.
They were members of the Moon Coven, a gathering of witches formed during the Walpurgis Night's glory days. It was created to prevent the "truth" from spreading in the world. Morgan Le Fay, the Great Matriarch, delved into forbidden knowledge that couldn't be uncovered no matter what.
Le Fay was investigating the calamity, and it's said that her research made some progress. However, she perished before she could uncover the truth—the hidden truth about the so-called "Rebels."
The Walpurgis Night was a small sacrifice to prevent a greater tragedy that could involve all dimensions.
Thanks for reading and I hope you like it.