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Hat of Storm Scion's Power
Hat of Storm Scion's Power
Uncommon
Thunderous Acuity: When the wearer deals Thunder damage, they gain Arcane Acuity.

Location - Hat of Storm Scion's Power
It is found in Act 2 - Moonrise Towers. Be sure to to infiltrate the tower first, and not attack the Absolute forces.
Look for a Drow trader named Araj Oblodra. She is the one selling it. You can find her in one of the rooms on the left as you enter the fortress.
Discussion
Arcane Acuity
Affected entity has a +1 bonus to its spell Attack rolls and spell save DC for each remaining turn.
Reduce the duration by 2 each time the entity takes damage.
Arcane Acuity has a maximum Duration: 10 turns.