If the monsters are too hard for you, such as if a monster spawns during a harder Lifestream setting and you can not kill it you can use a Templar Beacon to despawn the monster.
To do this you must have first completed the quest from the Knights Templar to gain the Templar Beacon, you can then use it as much as you want to despawn whatever nasty monster you come across (either your monster or someone elses).