Ashe's Aura of Invulnerability

you extend an aura of protection to keep those near you safe, until the spell ends when a creature that you can see within range takes damage you may reduce that damage by an amount equal to 5 plus your Charisma modifier if you do then you take damage equal to half the damage prevented (rounded down) this damage cannot be reduced or negated in any way and it does not trigger concentration checks.

when you cast this spell with a spell slot of 3rd level the duration increases to 10 minutes, when you cast this spell with a 4th level slot the duration increases to 1 hour, when you cast this spell with a 5th level slot the duration increases to 8 hours