Use Eat Memories ability the same amount as proficiency level per day for proper stack effects. Which are highly effective at Tier 2 (levels 5-10).
The Action: As an Action, Creature forces a DC 13–15 Wisdom Saving Throw (adjusted for level 5).
Failed Save: The character takes 2d10+3 psychic damage and becomes Memory Drained until they finish a Short or Long Rest or are targeted by Greater Restoration.
The Penalty: While Memory Drained, the target must roll a d4 and subtract the number from any ability check or attack roll they make.
Cumulative Effect: If they are drained again before resting, the penalty increases (d4-d6-d8-d10-d12-d20).
Character Gains the Target's Languages.
At Tier 3 You Gain Target's Proficiencies (except saving throws).