be at the mercy of (something/someone)

to be in a situation in which you cannot do anything to protect yourself from something or someone unpleasant.

Poor people are increasingly at the mercy of money-lenders.

Of course, in a tent, you're at the mercy of the elements.

• You can't say fairer than that.
• You can't teach an old dog new tricks.
• You can't win 'em all.
• you could cut the atmosphere with a knife
• You could have heard a pin drop.
• You could have knocked me down with a feather!
• You could have knocked me over with a feather!
• you could hear a pin drop
• you couldn't have asked for anything more
• you couldn't have asked for more
• You could've fooled me.
• You'd better believe it!
• you don't need this
• you have got to be kidding
• you haven't lived
• you haven't lived until
• you haven't lived until something
• You have to be cruel to be kind.
• You have to hand it to
• You have to hand it to someone
• you know
• You live and learn.
• You'll catch death!
• You'll catch death of cold!
• you'll catch it