Astral Brace of Cloak

This is a metal and leather arm brace that clasps around the wearer's arm. On the front is a small plate of obsidian-like material that glows blue when touched. The wearer has to be able to press this plate to activate its ability. 

Once per long rest, this item can be used to make the wearer and any carried belongings invisible. While invisible, they cannot be detected by sight alone, unless aided by magical means. This effect lasts 3 rounds, or 10 minutes out of combat. If the wearer attacks or is attacked, in or out of combat, the effect ends early. Attacks made against the wearer while invisible suffer disadvantage, and initiative rolls made by the wearer while invisible benefit from advantage.