the living dead! (skeletons, vampires, zombies etc)
-Too cliche. Also, vulnerabilities too well known.
pirates!
- Too concerned with looting and wenches to appreciate intricate mission of sublety
animorphs
- NO. just... No.
human raiders
- Humans in general are squishy and can be bribed/scared/persuaded to betray you. Also, see Pirates.
sorcerers
-This might be good, but weak sorcerers are of no use and strong sorcerers tend to be ambitious: possible revolts in army of Darkness are not acceptable.
demons
- No loyalty what so ever and do not care if the person screaming is you or your enemy. Powerful, but unreliable and backstabby.
massive monsters
- Logistics nightmare. No sublety.
other
- by definition, this. If only I could imagine what it might be... Brainwashing techniques can be countered, copies of myself might simpy overthrow me, mortals are squishy bags of flesh, summoned creatures...
... might actually work. Do yourself what needs doing, for large scale engagements summon an army of magical spirits, elementals, fantastic creatures etc dismissable by a wave of your hand if required, enforced loyalty almost guaranteed (as long as you don't go summoning anything too big and bad). Excellent casualty tolerance, minimal logistics and support requirements, always accessable if needed.