Dynamic Stature

You know the Enlarge/Reduce spell and can cast it once per Long Rest with an optional additional effect based on the option used.

When a target of the Enlarge option uses the Grapple or Shove option of its Unarmed Strike, creatures smaller than it have Disadvantage on D20 Tests made to avoid the effect.

A target of the Reduce option doesn't provoke Opportunity Attacks from creatures larger than it.