Strength of the Wither spell: Damage dealing

Does anyone know about the source of power?

I read this on some Stratics thread (sorry did not bookmark):

* Spell Damage Increase
* Not: Slayers (from spell books; I would not have expected talisman or weapon slayers to work anyway)
* Possibly: From the Int stat?
* Spirit Speak
* Stratics people think that Necromancy does not count for damage dealt by the Wither spell

Can anyone verify that?

Wither Tiles change

As it is reported on Five on Friday - October 24, 2008, Wither range is not anymore 5, but 4 tiles. --Daedalus 14:11, 3 July 2009 (UTC)