Plot hooks are tough. I try to float out a selection of possible villains but I sometimes run into the “What happened to that evil aboleth?” question. That’s when I introduced rival adventuring groups. I use them as an excuse whenever my group decides to ignore the evil gods in favor of opening a pet grooming salon.
Has anyone introduced rival groups? How did your party react? Mine formed an irrational hatred for them even though their rivals are only ever nice!