|Full Name||Marissa Adrina Thompson|
|DOB||July 26, 1997|
|Mortal Parent||Harrison Thomson|
|Years at Camp||5|
|Fatal Flaw|| Holding Grudges
- "Normally, I'd be mad at the person who found out.. it, but I'm not mad, I'm just.... scared."
- ―Marissa to Brent Miller
Marissa was born on July 26th to Hecate and Harrison Thompson, a magician. When Harrison first met Hecate, the two didn't get along at all, and they rivaled magic shows like crazy. At one point, Hecate got so mad she used her real magic in her show, and Harrison fell for her. Hecate forgave Harrison, and the two got married.
Marissa's fatal flaw is her ambition. She wants to have power, and she wants everyone to respect her like a queen. This fatal flaw has gotten to her head, and that is why she is a spy for Icarus.
At a young age, Marissa was not very fond of school. She was brought to camp at a young age, but does not remember much during those times. One day, when she was 9, she was swimming, when she got lost at sea, and swam to the magical pool, on the night of a full moon. She now grows a tail ten seconds after touching water. When she was 14, she, along with the rest of her brothers and sisters, joined Luke Castellan and the titans. She had been on a boat, when it had been attacked by members of Camp Jupiter. She jumped overboard and swam away from the boat as a mermaid, therefore making her the only survivor of that boat. When the Titan War was over, she was pitied and brought back to camp, much to her dismay. She made a secret alliance with Icarus, wanting revenge. She is currently his spy, but nobody else knows that.
Marissa has brown hair and brown eyes. As a mermaid, her tail is orange, and her hair has orange streaks in it.
- Everyone else at Camp Half-Blood.
- Marissa grows a tail ten seconds after she touches water.
- Marissa uses a sword.
- Marissa can stay underwater for about twelve hours.
- Marissa can bend the Mist to her will.
- Marissa can Siren sing.
- Marissa has Mistforms, but hardly ever uses them.
- Marissa is a spy for Icarus.
- Marissa can resist a lot of damage done to her.