Need help with Undead

[Cyussu]

Ok, and I presume ahead of time it /doesn't/ exist...But is there a way to increase an Undead's HD AFTER it's been created? I'm playing a 6th level Dread Necromancer Catfolk (Mm...dat Cha & Dex...) that's using a Spell Storing Xbow focused on keeping my TWO, yes TWO, Undead alive from afar. I haven't decided on what I wanna make an undead of yet, and curious if, at all, you can actually update their HD to keep them "on par" with the max HD I can apply and keep without going over the max. If there isn't, then I apologize for wasting anybody's time...

[Scheming Wizard]

Not that I know of. There are spells that can make your undead stronger like this one http://dndtools.pw/spells/spell-compendium--86/stone-bones--3922/

As you level you will get access to higher level create undead spells that will let you create stronger undead. Intelligent undead like vampires can take class levels and keep up that way. Libris Mortis even has Ghouls and Mohrgs taking class levels. You will probably have to work that out with your dm though.

Templates are also an interesting idea. The evolved and spellstiched templates also make undead stronger, but again you'll need to dm permission to apply them. I think it would be reasonable to let a necromancer carve magic runes on his creations or let an undead that has been around for a lot of adventures evolve though.

http://www.realmshelps.net/monsters/templates/spellstitched.shtml

http://www.realmshelps.net/monsters/templates/evolvedundead.shtml

[Cyussu]

I guess I'm stuck until I can spawn Ghouls (Personal favorite due to dat Cha), and I can't get Stone Bones as a Dread Necromancer without using a Rod, which as a Dread Necro, I don't get UMD. Thanks either way, I'm already tugging at my DM's last string for mentioning a Necromancer, I told him I wouldn't, nor do I personally like, use an /army/ of Undead, only 2 maybe 3...

[Scheming Wizard]

I've never played a Necromancer, so I'm not really an expert on them. This guy has a pretty serious guide though http://community.wizards.com/forum/previous-editions-character-optimization/threads/1096381

[ShurikVch]

Make undead out of Dusk Giant or Maurezhi, awaken it, then feed it good?

Consider to select some of those feats:
Corpsecrafter (LM) - undead gets +4 Str and +2 hp/HD
Animation Mastery (Dr#298) - undead gets maximal hp per HD, and +2 turn resistance
Graveborn Warrior (Dr#312) - undead gets any bonus feat it qualify for
Improved Animation (Dr#298) - undead gets +1 HD, and +1 competence on attack & damage rolls

[Cyussu]

Make undead out of Dusk Giant or Maurezhi, awaken it, then feed it good?

Consider to select some of those feats:
Corpsecrafter (LM) - undead gets +4 Str and +2 hp/HD
Animation Mastery (Dr#298) - undead gets maximal hp per HD, and +2 turn resistance
Graveborn Warrior (Dr#312) - undead gets any bonus feat it qualify for
Improved Animation (Dr#298) - undead gets +1 HD, and +1 competence on attack & damage rolls

As I said, I am looking for ways to increase their HD...I already know all about the corpsecrafter line of feats and all that, but I wanna be able to keep my undead creatures on par with my level as a Dread Necro

[ShurikVch]

As I said, I am looking for ways to increase their HD...I already know all about the corpsecrafter line of feats and all that, but I wanna be able to keep my undead creatures on par with my level as a Dread NecroAwaken Undead spell:
Undead also regain any extraordinary racial abilities they had in life, such as poison or scent Both Maurezhi's Consume and Dusk Giant's Cannibalize are (Ex), so they will regain it (at least if they are not skeletal)

For each suitable humanoid corpse a maurezhi consumes, its Hit Dice, natural armor bonus, Strength, Intelligence, and base attack bonus each increase by +1.
For every 5 Hit Dice of sentient (Intelligence 3+) living creatures or every 20 Hit Dice of nonsentient living creatures that a dusk giant consumes, it gains 1 Hit Die.