Amulet of concentration

This Amulet can look like any necklace the character chooses. It can only change appearance once per long rest. 

The main purpose of this amulet is that it allows you to concentrate on 2 spells at the same time for 4 rounds(24 seconds). Once the second concentration spells is cast you have 4 rounds until the first spell ends.

This item can be upgraded to exalted but that magic is unknown for now.