Thieve's Outfit (5e Equipment)

Wondrous Item, legendary (requires attunement by a neutral or evil character)

When wearing these plain looking clothes, they will change to fit your form and preferences. Additionally, while wearing this, you get +3 bonus to any Deception, Investigation, Stealth, and Sleight of Hand skill checks you make.

Also, when using a thieves' tools, you can add +3 to that roll as well.