< off topic --- yeah I figured, the warning though still stands. Hopefully that never shows round here. >
If the Karsus Avatar (or wtf) spell is Level 12, I suppose a "Lesser Deicide" spell that would work on demigawds is Level 13.
So then there's a Mass Lesser Deicide perhaps a level 16. And working it on up some more, to replicate what the Spellplague did ...
Killing a Plane is tricky to measure.
The Draeden are sleeping/waiting out the Gawds, and one of them is either a layer of the abyss or the whole abyss.
They were assuming / "knowledge-ing" they could do so ... meaning to kill a plane is to un-do fluff assumptions that are 40+ years old and multi-editional.
Gate could bring in a Psion 7 / Planar Vanguard 10.
And that dude could have mindswapped with his psicrystal that's now a Genesis Demiplane.
So that's transporting a small and limited demiplane.
Gate + Linked + PowerWordKill + boosted even further = epic spell with a DC in the 60s.
And that's only killing a lowly level 17 npc (ho hum) demiplane.
otoh ... a psicrystal + the demiplane abiilty, are both (su) and technically don't work in an Anti-Magic Field.
Well targeted level 6 spell = dead demiplane.