I don't understand how these spells work
- The spell Command Undead targets one undead creature at close range. It allows you a degree of control over an undead creature. This varies based on whether the target is intelligent or not.
1) If the subject is intelligent, like a Lich, it's considered friendly. This means it's easier for you to use the Diplomacy skill to make requests.
If you try to give it direct orders to do something it normally wouldn't, you have to win an opposed Charisma check. This means roll a d20 and add your Charisma modifier. The target does the same thing, and if your check is higher, you win, and the target does what you said.
This is very similar to the Charm Person spell.
In addition, it will not attack you. I might refuse to do what you ask, but it won't attack. (It could still attack your allies, though)
2) If the target is a nonintelligent undead, like a zombie, then it gets no saving throw. You can communicate only basic commands, such as “come here,” “go there,” “fight,” “stand still,” and so on. It'll do something suicidal if you tell it to.
3) In both cases, you must be able to speak to the target to tell it things. And if you or your allies threaten the target, it breaks the spell.
- The Control Undead spell lets you target existing undead and control them. This is like Dominate Person, you don't need to convince them to do things, you just make them do it. When the spell wears off, they might be upset with you.
- The spell Animate Dead lets you touch a corpse (or multiple corpses) and turn them into zombies or skeletons that will follow you, or attack things, or stay and guard somewhere, you just tell them what to do.
In one single casting of Animate Dead, you can animate up to your caster level of HD of undead. Say you're a 6th-level witch, your caster level is 6, so when you cast Animate Dead, you can animate up to 6 HD worth of undead. So one 6-HD skeleton, or six 1-HD skeletons.
At any one time, you can control only 4 HD worth of undead creatures per caster level. Our 6th-level witch can control 24 HD worth of undead. If she had a huge pile of corpses, she could cast Animate Dead four times, each time raising 6 HD of undead until she hits her cap of 24 HD.
- The Create Undead spell is similar, but more powerful. Instead of only animating zombies and skeletons, you can (based on your caster level) create ghouls, ghasts, mummies, and mohrgs. The difference (other than those creatures being stronger) is that they are not automatically under your control. When you Animate Dead you boss them around, when you Create Undead you're just making them appear. They'll then do whatever they normally do in the wild. You do have the option then of casting Command Undead so you can either control them or talk to them.
- The Create Greater Undead spell functions like create undead, except that you can create more powerful and intelligent sorts of undead: shadows, wraiths, spectres, and devourers. Just follow the same rules as Create Undead with the differences listed in the Greater version.
The only one of those spells with a limit is Animate Dead. You can Create as many undead as you like (and can afford) and you can Command as many as you are able.
Does having undead servants require me to have an evil alignment?
Not at all.
Many of those spells have the [evil] descriptor, which many folk believe make it an evil action to cast. In most cases, however, whether the act affects your alignment depends on the reason you're doing it. Are you creating an army to torment the souls that have passed beyond and using their bones to terrorize their families? Evil. Are you using your fallen enemies to help defeat the villains who want to destroy the world? Not evil.
It's a REALLY good idea to talk to your DM about that first, though. Even in PFS.
So creating undead could potentially become a problem, is there a way to make it permanent, or is animate undead the only one that is really viable?
Create undead IS permanent. I'm not sure what you mean by viable.
If you create some nonintelligent undead, then use command undead, they'll do what you want. At level 12 when you get create undead, that's 12 days per casting of command undead, or 24 days if you extend it.
Oh I get it. So I would use command undead, and if I tell them to go into a fight that the odds are against them, or something else that they wouldn't normally do then I do a charisma check to see if I can convince it.
Yes, but only if the undead you're casting on is intelligent.
Nonintelligent undead are mindless, like normal skeletons or zombies. They automatically do what you say, even if it's dumb.
Intelligent undead, like a lich or vampire, needs to be convinced via Charisma check.
Otherwise I would need to use the charm hex or control undead for it to actually do that thing.
The Charm hex is a mind-affecting charm effect. Undead creatures have Immunity to all mind-affecting effects (charms, compulsions, morale effects, patterns, and phantasms).
A single casting of Animate Dead can create DOUBLE your caster level in undead hit dice (four times if under a desecrate spell).