Disrupt Undead Options

[Sikret]

The idea of this new necromantic spell was originially introduced here as a 6th level spell. Later, I realized that having it as a 6th level spell is not a great idea for some reasons:

1- There are already too many good 6th level spells in the game.
2- The spell seems a bit too powerful to be 6th level

I didn't want to abandone the idea of this spell; so, I now return with a new proposal to add it as a replacement for a higher level spell. I also changed its name after reading the suggestions and opinions about the name.

The spell's new description is this:

Disrupt Undead (Necromancy)
Level:?
Range: Touch
Duration: Instantaneous
Casting Time: 7
Area of Effect: One Undead Creature
Saving Throw: None

By means of this powerful spell, the mage uses his powerful necromantic touch to disturb the negative forces floating inside an undead creature. The spell bypasses the target's magic resistance (if any) and inflicts a huge amount of damage, which varies depending on the udead type:

Skeleton Lords (and lesser undead creatures): 10D8

Skeleton Warlords: 8D8

Skeleton Grandlords: 6D8

Liches, Master Vampires and Vampire Lords: 5D8
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Tell me your opinion about the spell's appropriate level and the spell you suggest to be replaced with this new spell.

Some ideas which occurred to me:

(1) 9th level; replace "Gate"
(2) 8th level; replace "Symbol of Death"
(3) 8th level; replace "Summon Fiend"

If you think that the spell can be 9th level, I may even consider chaning the damage dice type to D10. What do you think?