expression
at the mercy of; as one is led by
Describes a situation where someone or something is left to the will, actions, or forces of another, without resistance. Often used with verbs like される or 任せる.
彼は運命のなすがままに生きた。
He lived at the mercy of fate.
風のなすがままに帆を任せた。
They let the sail be at the mercy of the wind.