Chesty took one arm of the mummy in cast it can be used for magical endeavors. The mummy was also wearing an amulet bearing the symbol of The Necromancer that members of the part from before Chesty joining up encountered with the guard captains on the mountaintop Temple of The Necromancer.
Other party members warned Chesty not to keep the amulet but to destroy it. Chesty put the amulet and the mummy arm in the Portable Hole, but not together.
SEE ALSO: Control Amulets