Note: This will not word if you have completed the quest "Whom Gods Annoy".
In Leyawiin go to Rosentia's house. There you will find four everscamps.
They are very weak and will never run out, so you can continue to kill them with one hit with anything as long as you are fairly strong, but if you're not, they can fight back which can also improve your skills.
Killing the everscamps is not breaking the law as long as you don't accidently hit Rosentia. As long as you did not complete the quest "Whom Gods Annoy", you will always be able to do this.