Slave cost for Soul Contract

[PhilD]

Endoperez said:
It might be that the forging needs the full amount of gems/slaves when you choose what to forge, (e.g. you can't forge a Dousing Rod if you have 4 slaves), but only subtracts the correct amount of slaves (if you had 65 slaves, you'd have some left over). This quirk existed in DomII, and might not have been fixed.

Well, I had hundreds of slaves when I tried forging; I only noticed that the amount of remaining slaves decreased by exactly 65 in spite of the forge bonus.

If it is supposed to have an unreduceable cost, fine - but the description, and the manual, should say so. AFAIK, they don't.