How about placing the coffins in some kind of death chamber?
Anyways, I have an applicant for consideration:
Name: Nashonluslem, aka Bloodypuzzle
Gender: Pick one, if I die, somebody else can take over my name and my work
Profession: I work with levers. I create devices, and the mechanisms used in the devices. I also create and place traps. Now, perhaps one of your minions would like to pull this lever? Come one, just pull the lever...
Reason for wanting to hench with us: To create beautiful devices of self-illumination, of course. Perhaps your guests would like to stay in one of my luxurious rooms, with complementary beef wellington? Just step over here, right next to the barrel with the food in it. Never mind that glint of metal. Yes, just a little closer...
How do we know you're not a spy? Just like you, I work for a higher goal than wealth or power. And if you're at all dissatisfied with my work, feel free to kill me and give someone else my name. After all, it's the work that's important, not the person. Besides, everyone else wants me dead, though it's not my fault. I didn't make them do anything...
What I suggest: We create traps where people chose their own fate.
Pull this lever, and they can leave without harm.
Pull that lever, and a dozen crossbows fire into them.
Tell them, "Feel free to grab a platinum goblet on the way out."
Then, after they grab the goblet: "What, you're having trouble walking while skewered on that spike?"
Freedom of choice! The best form of chaos!