I've seen the non-nerfed Hunter of Heroes laugh at a Wraith Crowned EA Demonbred, easily kill all the undead, then the Demonbred itself. The same Demonbred had killed the HoH easily when using a Spirit Helm -- the HoH is not lightning resistant... but it has Blood Vengeance (as do all Doom Horrors other than Scabiel), so low-level undead will easily maim themselves when attacking as the HoH.
A Phoenix Rod would also work, because they also lack fire resistance.
But yes, Petrify is a lethal pick if possible, and has the advantages of not needing gems and also being reasonable for normal battles. Magebane and the Infernal Sword also have unresistable effets, and Magebane has the further edge that it'll boost your MR so you have a chance of surviving the Consume Soul attack and of bypassing Blood Vengeance. Magebane will horror-mark you, but with it, you shouldn't have to hard a time of surviving them.
Ark -- needs to beat high MR, does very little damage per turn (you want to KILL it -- not disease it, blind it (may not even need eyes, can't remember), or do a piddling couple of hp).
Otherwise... you want precise, non-MR-based damage. High level Blood has two unresistable "send them to Hell" spells. Against two of Umor's forms, Astral would also be an important flag. That... or Returning.