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The second route is the spectre/wraith/shadow horde. The spectres are nice because a hit from them bestows two negative levels, which suggests a round or two to kill a commoner. In a deep sewer, desecrated, with a shrine to... $evilGuy, haul the homeless, travelling merchants, and other people no one will miss. In that place, your incorporeal undead should nom on the living. Specifically, your "leader" of the city should turn people into wraiths/shadows/spectres. By having a very flat hierarchy, you introduce a flaw into your system (single point of failure) but make it very hard for groups of your minions to be uncontrolled. If you're going this route, you'll want to target every city of a kingdom simultaneously. To do this, you'll need to have the Necrotic Cyst and the ability to cast Necrotic Tumor. That way, you can turn high-ranking people inside the prisons, government, and clerical orders before starting this plan. Then it's a simple matter of funneling the city's undesirables to the desecrated zone until you have, roughly, a spectre per household. Then pull the trigger as the sun goes down. After a few minutes, you'll have converted most of the kingdom. So long as you've necrotic tumored enough clerics and wizards, anyone who's managed to resist can get slaughtered by their "friends." If doing this on a long term plan, don't forget to build hospitals, orphanages, and tenements.

The second route is the spectre/wraith/shadow horde. The spectres are nice because a hit from them bestows two negative levels, which suggests a round or two to kill a commoner. In a deep sewer, desecrated, with a shrine to... $evilGuy, haul the homeless, travelling merchants, and other people no one will miss. In that place, your incorporeal undead should nom on the living. Specifically, your "leader" of the city should turn people into wraiths/shadows/spectres. By having a very flat hierarchy, you introduce a flaw into your system (single point of failure) but make it very hard for groups of your minions to be uncontrolled. If you're going this route, you'll want to target every city of a kingdom simultaneously. To do this, you'll need to have the Necrotic Cyst and the ability to cast Necrotic Tumor. That way, you can turn high-ranking people inside the prisons, government, and clerical orders before starting this plan. Then it's a simple matter of funneling the city's undesirables to the desecrated zone until you have, roughly, a spectre per household. Then pull the trigger as the sun goes down. After a few minutes, you'll have converted most of the kingdom. So long as you've necrotic tumored enough clerics and wizards, anyone who's managed to resist can get slaughtered by their "friends." If doing this on a long term plan, don't forget to build hospitals, orphanages, and tenements.

You'll also want a cadre of significantly less stealthy crypt chanters. Getting the first one will be very tricky. With a stretch (a very big one) you can grab the mantled erudite ACF, take the natural world mantle, and use the suggested "substitute powers" pseudo-acf in minds-eye to swap earthquake for greater shapechange. Unfortunately, that will have to wait until level 19 for it to be of any utility. It might be worth dipping into a PrC which provides the animal domain, which allows you to get shapechange when the ur-priest reaches 9th level spells. (level 15-16, depending). Crypt chanters have an excellent chance of enthralling huge groups of organised opposition, and eventually converting them into more crypt chanters. You'd want to have a chorus of at least 4 of them before trying to convert any sizable forces, but if you have a brass band of them singing row-row-row your boat (with a portion stopping every round to reset the saving throws), they are exceptionally hard to beat. If you issue your forces with wands of dispel magic to dispel death wards, you can use quantity to wear down even the scariest of Pelor's clerics. (Beware the ablative zombie bunny hordes!)

Level 14 allows you to metamorph into a Mohrg, which will allow you to animate as many zombie rabbits as you desire. Since there's no cap, It's an excellent way to build a huge army of rotting fur and cuteness. There are benefits here, too. Zombie rabbits (and other cute animals) will cause people to leave the countryside and increase the population of cities. Therefore, you can use your "zombie threat" to both scare off villages, lull your enemies into a false sense of security (who wants to be hired to vanquish zombie rabbits?), and concentrate your primary food where you want it. With that said, there's nothing stopping you from doing the same to dragons, but the world takes zombie dragons far more seriously.