In a large bowl, stir together the Greek yogurt, mayo, pepperoncini juice, ranch seasoning, and black pepper until smooth and creamy.
Add the shredded chicken, celery, and diced pepperoncini. Fold everything together until well coated.
If the mixture looks too thick, add another splash of pepperoncini juice until creamy.
Taste and adjust, adding more pepperoncini juice for tang or more pepper for bite. Chill if you have time.
Serve with crackers or piled on toast.