Focused mind

Prerequisite: the ability to cast spells
Your mind is so focused that you can concentrate on more than one spell simultaneously. If your spell casting ability is 16 or higher, you can concentrate on 2 Spells, if it is 20 or higher, on three spells.
When you take damage, you have to make a separate saving throw for every spell you are concentrating on. 
If you have the war caster feat, the advantage only applies to one spell (your choice).