The Xanathar (a clueless, know-it-all, silly beholder with a pet goldfish) captured an adventurer and gave the adventurer the following list of ideas for a backstory with some entries that it pulled from a handbook for players. The Xanathar demanded a complete backstory based on the information.

(IOW, this is all from dice rolls on tables in the PHB and XGtE. I would not recommend this method because it seems to me to have too many ideas for fleshing out a detailed backstory which can impede building a cooperative "forestory" with a group, but let's have some fun with it regardless.)

What level 1 backstory would you make out of this if a crazy beholder was holding you captive until you created one?

• • Name: ? <- (up to you)
  • Stout Halfling Monk (XGtE for race and class, odd/even for PHB subrace,)
  • Level: 1
  • Background: Criminal (XGtE "Occupation" - would have re-rolled if Adventurer occupation)
    • Specialty: Enforcer (PHB)
    • Feature: Criminal Contact (from Criminal)
  • Alignment: Lawful Evil (from Ideals, Lawful-Chaotic from XGtE)
  • Faith: ? <- (up to you)
  • Gender: ? <-
  • Hair: ? <-
  • Eyes: ? <-
  • Skin: ? <-
  • Size: Small (from Halfling)
  • Age: 72 (rolled XGtE age, rolled within range, x1.5 to scale vs. Human age)
  • Height: 3' (PHB)
  • Weight: 40 lbs. (PHB)
  • Personality Traits:
    • I always have a plan for what to do when things go wrong. (PHB)
    • I am incredibly slow to trust. Those who seem the fairest often have the most to hide. (PHB)
  • Ideals: Greed. I will do whatever it takes to become wealthy. (Evil) (PHB)
  • Bonds: My ill-gotten gains go to support my family. (PHB)
  • Flaws: An innocent person is in prison for a crime that I committed. I’m okay with that. (PHB)
  • Appearance: <- ?
    Everything that follows is from XGtE unless specified otherwise.
  • Monastery: Your monastery was founded by gnomes and is an underground labyrinth of tunnels and rooms.
  • Monastic Icon: Hydra. Your order singles out the hydra for its ability to unleash several attacks simultaneously.
  • Master: Your master was cold and distant. You suspect that the two of you might be related.
  • Origins
    • Parents: You know who your parents are or were.
    • Father: (Even/Odd gender)
      • Class: Bard
      • Occupation: Artisan or guild member
      • Alignment: Neutral
    • Mother: (other gender)
      • Class: Cleric
      • Occupation: Farmer or herder
      • Alignment: Neutral
    • Birthplace: Home
    • Siblings: 4
      • Sibling 1:
        • Birth Order: Older
        • Occupation: Merchant
        • Alignment: Neutral Good
        • Status: Alive and Infamous
        • Relationship: Friendly
      • Sibling 2:
        • Birth Order: Younger
        • Occupation: Farmer or herder
        • Alignment: Lawful Evil
        • Status: Alive, but doing poorly due to injury, financial trouble, or relationship difficulties
        • Relationship: Friendly
      • Sibling 3:
        • Birth Order: Older
        • Occupation: Criminal
        • Alignment: Neutral Good
        • Status: Alive and well
        • Relationship: Friendly
      • Sibling 4:
        • Birth Order: Older
        • Occupation: Artisan or guild member
        • Alignment: Neutral
        • Status: Alive, but doing poorly due to injury, financial trouble, or relationship difficulties
        • Relationship: Friendly
    • Family and Friends:
      • Family: Mother and father
      • Family Lifestyle: Poor
      • Childhood Home: Rundown shack
      • Childhood Memories: I had a few close friends and lived an ordinary childhood.
  • Personal Decisions:
    • I became a criminal because ...: I fell in with a gang of reprobates and ne’er-do-wells, and I learned my specialty from them.
    • I became a monk because ...: I was wild and undisciplined as a youngster, but then I realized the error of my ways. I applied to a monastery and became a monk as a way to live a life of discipline.
  • Life Events:
    • Life Events by Age: 4
      • Life Event 1: Boon: A relative bequeathed you a simple weapon of your choice.
      • Life Event 2: Boon: You found something interesting. A tiny gnome-crafted music box that plays a song you dimly remember from your childhood (Trinket: PHB)
      • Life Event 3: Tragedy: You lost all your possessions in a disaster, and you had to rebuild your life.
      • Life Event 4: You fell in love or got married. Work with your DM to determine the identity of your love interest.

On that last one, feel free to do whatever you wish to created the identity of the love interest or leave it as-is. There are things missing such as sibling gender and more, but they were not part of the XGtE recommendations. That's all left up to you. (Note: It does indeed have "Alive and infamous" for that one NPC.)