Nonetheless, the undead would like to conquer it.
Presently, the undead who would like to conquer it is Kolothure Hellblade, one of the many independent warlords in Ustalav, who was not, actually, one of the undead at the Conclave of the Way, a fact that might, under some circumstances, prove important. That was the former master of her forces, ancient nosferatu-vampire Vilyer; the Hellblade was not at the meeting because she was dead, the enchanted adamantine armor bearing her soul floating in a vat of acid - also courtest of Vilyer. The vat, not the soul.
Let's back up.
Born of a mortal man and a champion of Hell, the Hellblade forsook her infernal heritage for the simple task of engaging in as much brutal warfare as is possible, abandoning lord after lord as soon as their wars were concluded to seek out another to whom she could turn her sword, ultimately transforming from mercenary to warlord around the same time Gorum made her His chosen, thanks to running out of battles to fight. When she was finally put down her raging spirit did not depart her body, and though aeon after aeon she was slain, each time her spirit rose again, clinging to the indestructible armor that her patron had blessed for her so that she could live again.
So, when an oath required all undead to unleash their secret weapons upon the world, Vilyer, who already had her corpse sitting in his laboratory, provided her with a highly expendable army, magic items, drained the acid from her containment tank, and hightailed it over to a backup fortress to work on his next plot against Lastwall before she decided that he would be more interesting to murder than whoever was running Carrion Hill today.