Marissa Baelish is a member of House Baelish of the Fingers, a cadet branch of House Baelish of Harrenhal. She was raised in House Baelish's tower in the Fingers of the Vale of Arryn by her parents, alongside her two sisters, Emphyria and Elaena Baelish.
She is the most adventurous and mischievous of the three Baelish sisters, often teasing and successfully riling her eldest sister Emphyria.
Marissa was born in the Vale.
With the mounting tensions and conflicts due to the Sistermen Rebellion, Marissa and her family are sent to stay in Gulltown for the duration of the conflict. Her father, Tybolt, stays behind to defend Baelish lands in the event that Sistermen begin attacking the coast of the Vale.
Whilst in Gulltown, Marissa inadvertently befriends Lord Ronnel Royce and attends House Grafton's banquet to celebrate the end of the Sistermen Rebellion. Her family narrowly avoid social scandal after a physical altercation between her eldest sister Emphyria and Lord Grafton's heir, Theo Grafton.