I am looking for advice. I want to create a destructible sigil stone, and my current plan is to make it into a creature.

My ambition is to use PikachunoTM's sigil stone mesh and Bethesda's heart of lorkan mesh as the base. It already has an interesting death animation, but all that I really want is a way of meeting whatever animations requirements morrowind has of a creature. Is there any way to use NifSkope to achieve such a feat, or is this going to require a tool such as blender?

Hmmm... I might be wrong but I believed you can use basically any mesh as creature model, it will just not have any animations, but that seems to be what you want. So have you tried simply using the sigil stone mesh?

EDIT: Or perhaps it needs Root bone, but that should definitely be it. And it should be doable with NifScope only.

I already tried that to no avail. When I tried to simply use the non-animated NIF I got the following error.

Creature "aa_sigil_creature" has no animation groups.
Morrowind will crash!

Continue running executable? Cancel is "Yes To All".

What I am trying to do is figure out what animations are required -- perhaps it simply require any one animation -- and ideally i could modify an existing creature to serve this purpose.

This sounds interesting. Might I ask what you are planning to do with this?

Can you upload or give link to the sigil stone model?

I'm building a dungeon with enemies who respawn until a sigil is destroyed. I liked the idea of destroying the sigil stone through combat, as opposed to Oblivion's loot-able item.

Daedric Resources by PK Chuno : http://www.nexusmods.com/morrowind/mods/44205/?

In particular m_Sgl_Stn3.nif

Gotcha. I agree, I like the sound of that.