Beatrice had a special method to track down someone who had killed her family members. And using that technique, she was able to track down the Infernal Fiend without any problem. But while being on the run from Elena, the Fiend had teamed up with two other boss level enemies. Even for Elena, defeating all three of them alone was extremely hard.
Not only that but this Infernal Fiend had marked all the people of the city where Elena currently was with his mark. So if anyone from his same power level was not inside the city to cancel the mark's effect then this Infernal Fiend would be able to kill off all the people in no time. So Elena was forced to stay inside the city until she could dispell the mark from all the citizens.
