Twilight Zone

You Enchant a Glass Shard, it turns opaque similar to Obsidian. When thrown on a surface a portal is opened to the Twilight Zone, an inter-dimensional space between matter. You can see black when in here, for you are between molecules. If another creature enters the Portal, they can not see anything, but you can see them perfectly. The Portal lasts for two turns, after which you can use the Vocal command to exit the portal. You are impervious to attacks from outside the portal, but within you have a disadvantage on all rolls.

If the Glass Shard is not thrown in 2 turns it looses it's power and breaks apart.