Mildness.
Mildly.
Moderate; kind; calm.
Larry regarded his friend in mild surprise. – The U.P. Trail by Zane Grey
This is mild; that harsh. – Burke's Speech on Conciliation with America by Edmund Burke
Quite an old- world girl, I declare; sweet, and mild, and gentle... – More About Peggy by Mrs G. de Horne Vaizey