Lars Battle-Born is a child living in Whiterun. He gives the Bullying Braith quest.
Lars Battle-Born can be found in Whiterun walking around, and possibly, being bullied by Braith. He can also be found inside the Battle-Born Clan Hall. If you complete the miscellaneous quest Bullying Braith, you will no longer see him being bullied by her. His dialogue will also change to him thanking you, now that Braith will not bully him, even not look into his eyes.
If the player casts spells in front of Lars, he will get excited and ask the player to turn him invisible. Since there is no invisibility spell to cast on others in Skyrim, your only options are to turn him down or to lie and pretend that he is invisible. This effect has been seen elsewhere on other children, such as Assur, the Jarl of Winterhold’s son.