The Shadow Orb, is an item that had been thought lost in the world of Nerith. 

It's creators are unknown, as is it's original use. What is known, is that twice, until a long rest, the orb can cast the spell, no attunement is needed, while concentration by the holder is also needed. This power only works in darkness and shadow. 

As per Pass without Trace:

"A veil of shadows and silence radiates from you, masking you and your companions from detection. For the duration, each creature you choose within 30 feet of you (including you) has a +10 bonus to Dexterity (Stealth) checks and can't be tracked except by magical means. A creature that receives this bonus leaves behind no tracks or other traces of its passage."