Amulet of Concentration

This platinum chain is adorned a flat, mulitfaceted, polished onyx stone.  A slight humming in the air sounds when it is touched by a magic user.

This amulet requires attunement and has 3 charges.  At the cost of 1 charge, it grants the wearer the ability to concentrate on two spells at once.

When not concentrating on two spells, this amulet grants advantage on Constitution savings throws to maintain that concentration. While you are concentrating on two spells, that savings throw DC increases by 5.  The first spell you are concentrating on, dissipates after 12 seconds (two rounds).

Notes: Advantage: Constitution Saving Throws, Short rest