Abyss monarch cookie doesn't feel like a legendary not because of their story but because of the execution. Throughout all their screen time in the wandercrab cutscenes, it just felt like they were a cookie living in the city who just so happened to be an all powerful sea deity instead of an all powerful sea deity that just so happened to be living in the city. It would've been a lot more interesting if they really pushed the fact that they were some type of folklore to deep sea cookies and maybe even give them a small following of sea monsters to really push the fact that they were the abyss monarch. Thanks to their whole in cloak cookie persona being shown more than their real self, they just felt like a massive let down.