The Sacrifices are the ten body parts needed to perform a resurrection ritual, such as the one performed on William Vanderboom. It is strongly implied that these sacrifices must come from family members of the person to be resurrected. However, it seems that in-laws count, as neither Mary nor Ida is related to William by blood.
The ten sacrifices, and the characters who donated them to William, are as follows:
See also: Sacrifices/Gallery