A vicious animal attacks you on a moonlit night. Friends drive the beast off, but you discover that you've been cursed with lycanthropy, to become a similar beast under the full moon. (work with your DM to determine details)
In adulthood you have an encounter with an unusual person, who as far as you can tell, has no home or family. You offer to help in anyway you can. After accepting your hospitality the stranger vanishes leaving a note "Your kindness will be remembered".
was foraging or hunting for food, They had an encounter with a trapped predatory beast. Instead of slaying it, they freed it. The freed beast then disappeared. Later, they were trapped by a falling log. The same beast reappeared, aiding and freeing them.