Adamantine Lockbox of the Arcane

This small hand-sized lockbox has polished silver bands with arcane writing and sigils. 3 hinges of the same are visible on the back. There is no visible lock and is sealed airtight. Can be forced open with a DC 25 strength check. Upon a failed check, the target must succeed on a DC 18 Constitution saving throw or be paralyzed for 1 minute. The box has an AC of 25 and 50 hit points. Regains 1d8 hit points every hour. Once forced open or destroyed, loses all magical properties.

Notes: Once attuned, this box will open and lock itself at the will of its owner. Attunement fades if owner is killed or removed from the same plane of existence. Can be opened freely if no one is attuned to it.