The phrase "were at mercy of" implies that one party has complete control and power over the other. Synonyms for this phrase include "at the whim of", "under the power of", "subject to the dictates of", "dependent on", and "vulnerable to". These words convey a sense of helplessness and lack of agency, highlighting the fact that the situation is out of the victim's hands. Other similar phrases include "at the mercy of fate", "at the mercy of circumstance", and "at the mercy of the elements". In any case, these phrases are all indicative of a power imbalance and a lack of control or autonomy.