I respectfully disagree,sorcery or mysticism means in Dragonlance the Sorcerer or the Mystic class....
I looked a little bit when thinking about taking the feat for a Dread Necromancer I was building a little bit ago, and found no standard definition for Sorcery or Mysticism. It's entirely possible I was looking in the wrong place, though.
As for how to power it, I was going to use Wights. They're relatively difficult to control, but easy to farm and have decent HD for powering this. Keep one in an enveloping pit and throw in some commoners every one-and-a-while.
When it comes to keeping it under control, it's basically only
that good in the hands of an Undead Army Necro. If your necromancer is only planning on keeping one or two big, ugly skeletons/zombies around, and then use Undead Battery to recycle the old ones when he hits his control cap, then that's no big deal.