The Consume skill kills one of your minions and applies a buff to the Reaper for a base duration of 6 seconds. The buff grants 40% increased damage, 20% increased attack speed, 20% increased movement speed and 10% increased character size.
The Reaper has muliple instances of the skill which its AI uses in different circumstances:
- The version it frequently uses because it's hurt has a 6-second cooldown.
- The version it infrequently uses because it just felt like it (and didn't already have the buff) has a 25 second cooldown.
EDIT: Consume also recoverys 50% of the Reaper's life.