That's Sona, the older music focused hero, her kit is:

• Q - instant damage to 2 targets and bonus damage to next attack for people standing close to her, can't remember if that refreshed while you were standing in the aura or not
• W - heal self, someone else, and give shield in aura one per hero
• E - speed to self, one other, and less in aura
• R - stun and damage

IMO similar to Largo's R, but worse and you don't have to keep the rhythm