Servants/prisoners....explain? SPOILERS

[Skandis]

Well my memory is fuzzy as always, but here's what I gathered:

Spoiler below!

Alexander used to have a few human servants (at least his butler). Wouldn't suprise me if they partook in the kidnappings, as he did kill off a couple with the wine just to silence them.

As for the gatherers, maybe he needed to harness the power of the orb to actually get them working? For me, it seems like the gatherers are otherworldly spirits that can take over human bodies, provided that they've gone through the ritual properly. If he needed something as powerful as the orb to get them going, it wouldn't suprise me.
Remember that he broke the last orb he was given, so he might've even stocked up on a small supply of gatherers.

As for the gatherers not killing Daniel right off the bat:
They kinda do try to do it. They're not the wisest bunch though, so they seem to continually fail.