Unique Wolf Mermaid. Anna can be found in deep water tile events.
She and her unique Leviathan pet Bubbles are ambushed by some water creatures and you are given the option to help if you wish to recruit her. They will join you in the battle, which usually consists of 1-3 enemy Leviathans and some other water creatures.
They have an interesting mechanic. Anna's damage dealing potential isn't great, instead she plays the supporting role to Bubbles who normally doesn't gain any ap unless engaged. Anna has a unique skill, Command, which gives Bubbles 2 ap. Naturally this skill is crucial to utilize this powerful, unique pet. Additionally, the Command skills is inheritable, so you could create an entire team that can make Bubbles an enemy wiping machine.
She has one town event at the Beach, that will randomly trigger if she is level 10. The first option will give Bubbles the KnockBack and Consume skills, as well as increase his level cap to 25. The second option will give your main character the Command skill.