Spoilers for Game of Thrones, season 7 below.
Way back when Davos the Onion Knight was imprisoned on Dragonstone and Stannis Baratheon was still Melisandre's chosen regent, Shireen Baratheon went down to the dungeons with a gift.
She had a book for Davos, who shamefully admitted he couldn't read it.
"I'll teach you...! It'll be fun!" responded Shireen, who would later, um, get burned to death by Melisandre because Game of Thrones is horrible. And also because Melisandre thought it would ingratiate Stannis, the supposed chosen one Azor Ahai, with the Lord of Light. The bit of blood magic was used to pave the way out of a snow storm for Stannis' troops.