A Soul Reaper is a scythe that appears to be made of bones. The Soul Reaper can't be crafted, but can be dropped by a Harbinger or can be found in dungeons. When used as melee weapons, they cause 5-8 hitpoints of damage.
The only way to repair a Soul Reaper is with bones on an Anvil or by XP repair with the enchantment table.
The durability of the Soul Reaper is like the Stone Scythe's, the strength of it is like the Iron Scythe, and has a higher enchantability rating than gold.
Incidentally, the Soul Reaper happens to be the Harbinger's weapon of choice.
No other mobs have been seen with it.