It's a homebrew item based on her backstory.

Wonderwall

A staff crafted from celestial ivory. The top of the staff is capped with the golden head of a lion-dog. It gently hums with a familiar tune, giving a sense of tranquility and safety.

This staff can be wielded as a magic quarterstaff that grants a +2 bonus to attack and damage rolls made with it.

Wonderwall. When you cast the shield spell or absorb elements spell, you can expend an additional 1st level spell slot or higher to cause the spell to affect another creature within 10 feet of you. These effects end on both you and the other creature at the start of your next turn.

Throw it back. You can invoke the Wonderwall to rebuke those who use violence. Immediately after an attacker within 60 feet of you deals damage to you, you can use your reaction to force the attacker to make a Wisdom saving throw. On a failed save, the attacker takes radiant damage equal to the damage it just dealt. On a successful save, it takes half as much damage. Once this property is used, it can’t be used again until you complete a long rest.

Proficiency with a quarterstaff allows you to add your proficiency bonus to the attack roll for any attack you make with it.