Undead are welcome in Zigur

[Grey]

It looks like you can even take the anti-magic quest, though I wasn't crazy enough to try and see what happened with that... In general I'd say that undead, as creatures of magic (which the Ziguranth may be able to pick up on) should not have Zigur generated on the world map.

[Frumple]

They can take and complete the AM quest just fine, but it initiates uber-challenge mode, preventing use of all arcane items (include runes and, currently, the Cloak of Deception).

Here and here for earlier mentions of this.

Short for of my opinion: Make the cloak unknown powered, let undead get AM, give them access to infusions, perhaps weakened, on gaining AM. Fluff it as something equilibrium powered taking over for the magic. Undead already get blocked out of four classes, rather they not get blocked from even more build options. Nothing wrong with 'powered by sentient mold' becoming their new shtick.

[Madsamurai]

There is already the undead mold unique so there is precedent :p