Anti-Magic Collar

This prisoners collar is wrought in the dark-hued cold iron of the north, with faint silver arcane scrolling on the inside rim. It thrums with arcane power. When looked upon by a spell caster they have been known to feel it's presence as an endless hungry void.

Forced Attunement: In order to be attuned to this collar it must be placed around your neck and locked with it's matching key, at which point the collar instantly becomes attuned to you and you can not detune from the item unless the collar is either unlocked with it's matching key and removed or the collar is broken and removed from your neck. 

Magic Draining:  As long as you are attuned to this collar, at the start of your turn you lose your one of your highest level spell slots as the collar absorbs it from you and shunts the excess magic into the ethereal plane. While attuned you are also unable to use any spell-like magical abilities (Ex. a Divination Wizards Portent ability, a Warlocks Pact of the Blade ability, etc). In addition, while attuned to the collar you cannot gain new spell slots from any source.

Magic Suppression: While attuned to this collar all permanent magical effects affecting you are suppressed and considered ended until the collar is removed (Ex. a Sorcerers Draconic Resilience ability, a Warlocks Devil Sight Eldritch Invocation, the Blood Hunters Hunters Bane ability, ect)