The Siren is the Fear of failure and self-loathing. She is often considered to be the related to the The Mother of Snakes, as their domains and hunting mechanisms overlap. But where the Mother shows people what they wish they were not, the Siren shows them the exact opposite; an idealized image of what they wish they were, realizing all of their hopes and aspirations for a fleeting instant, taunting them with their failures and deficiencies. This actually makes her a far more dangerous Fear than the Mother, and she has driven countless humans to suicide.
She has a particular affinity for water, and while the Mother of Snakes tends to use mirrors to communicate with her servants and victims, the Siren relies on more ephemeral images, such as the reflective surface of water or her victim's dreams. Oftentimes, she encourages those she's taunted into taking their own lives to drown themselves in the sea, by tying their ankles together.
Her domain is the Vault of Tears, a series of glassy caverns deep below the waters. From there, she spreads her influence through the waters of the world, seeping into the minds of those who are prone to self-doubt or self-hatred. Occasionally, when she finds a soul afflicted by particularly delicious agony, she grants them a poisonous gift instead; their perfect life forever, at the cost of the flesh of others. These servants, her Drowned, are usually eloquent and irresistible; but water reveals them for the monsters they truly are.