How do i play a Necromancer Gravewalker & What do i need to know to control undead etc??

[Alesander]

In my campaign there will be a Wayang who works in the dark to find evidence of a demon scheming/starting a race war in the region the players will be involved in to gain power to be resurrected.

The Wayang is under a curse of this demon, which turned it into a wayang gravewalker from the fey sorcerer it used to be.
Iv made the character sheet. Its focused on being able to get away from combat with feats:
Spell focus Necromancer, Ability Focus Slumber, Extra Hex.
Not sure what Patron to use.
Traits: Stealth & disguise self to class skill traits.
Spells: Not sure other then Blend with surroundings so he can easily just "disappear" hide from players trying to kill him.

So if someone could list the things I need to know it be amazing.

The story in more depth if your interested.

He will appear to do evil things, but in reality he seeks knowledge and answers to stop a terrible demon to cause more trouble in the region.

The demon gave clues to some (not sure what race yet) to find a boss(not know yet) that seemingly protects a scroll. The scroll contains information leading to the group finding it starting a cult of superior races, to enslave or cleanse the weaker races in the region.

This information is obviously falsified to give the demon strength to use a bug in the universe to escape its prison in the underdark/darklands and into this realm to further wreak havoc and chaos.

One boss iv thought about is mad dryad. Having 200 feet radius of undeads around her with entangle.
Walking from graveyard to graveyard increasing her "domain" /Radius.

[VoodistMonk]

For a Gravewalker Witch, I highly recommend taking the Agent of the Grave prestige class.
Gravewalker Witch-6/
Agent of the Grave-5/
Gravewalker Witch-X

For feats:
1. Spell Focus (Necromancy),
3. Spell Specialization
Lesser Animate Dead (retrain to Animate Dead @ lvl 6)
5. Varisian Tattoo (Necromancy)
7. Extra Hex (Coven)
9. Extend Spell
11. Heighten Spell
13. Quicken Spell
15. Spell Perfection (Animate Dead)

[LordKailas]

I would recommend also grabbing the hex channeler archetype. It stacks with gravewalker and lets you pick up the feat command undead. Command Undead doesn't care about how many dice you roll for your channel so I wouldn't waste my time burning hexes to improve the channel beyond what you start off with.

As for a patron, gravewalker already gives you the spells you want so I would suggest looking at something that synergizes well with your aura. IMO the elements patron is a nice choice as it gives you shocking grasp which can now be delivered at range. It also gives you some other useful spells allowing you to do more than just debuffs.