I like this, and think that this is an interesting way that a necromancer could bind and control higher-level undead. It reminds me of the Genie-binding rules in the old Sah'ir's Handbook. The only downside I see, is I don't understand why the alignment must always be neutral. If I were an evil undead, being bound into this thing would just make me a pissed-off evil undead.
