My penance, constant in degree, is mutable in kind: one of its variants is tranquillity.

我的赎罪，程度不变，但种类一直在变：其中一种便是平静。

youdao

The hotel is a haven of peace and tranquillity.

这个旅馆是一个宁静的好去处。

《柯林斯英汉双解大词典》

You say she is often restless, and anxious-looking; is that a proof of tranquillity?

你说她经常不安宁，露出焦躁的神气：这难道是平静的证据吗？

youdao

It is also revered by tranquillity seekers.

BBC: In Puerto Rico, Culebra vs Vieques

The last thing I would want to happen is for the peace and tranquillity of the life that I enjoy here disrupted in any way.

BBC: Life on one of the world's most remote islands

The sound overlays abstract shots of water, rivers and sea, until urban congestion is wholly wiped away by Mediterranean tranquillity.

ECONOMIST: All that glitters