Reaper bonus

Named chest loot from quests run on Reaper difficulty has a chance to gain an additional enchantment from the following list:
 * Reaper Ability Boost: Provides 2 Reaper Bonus to all Abilities (found on helmets only). These are sometimes referred to as Reaper Hats.
 * Reaper Power Boost: Provides 3 Reaper Bonus to Melee, Ranged and Spell Power ratings
 * Physical Resistance Rating +3
 * Magical Resistance Rating +3

All reaper bonuses fully stack.

Warning: Some upgradeable items might lose their reaper bonus when upgraded, for example via Epic Crafting.

Unlike with Mythic Boost, item slot does not predetermine the type of bonus that you can get.

Occurrence Rate
Reaper bonus occurs on about 5% of eligible items in reaper mode, with a very small chance to occur in conjunction with another bonus. (Sample size: 211 items. Data source: Google Sheets)