Keith was always a grumpy merman. He, along with the Blade of Marmora, fought and defended the Merfolk's kingdom from predators and hunters looking for a tail and scales to sell. Usually, those hunters were Galran. Keith had taken down dozens of ships with the Blade, and this ship, at first, didn't seem to different. But when Keith did notice the differences, and decided to investigate, he regretted his decision. Greatly.
This is also published on Archive Of Our Own, under hnb65mnl, so if you've read that, I'm the same person. Updates will be at about the same time, they're the same story and shiz so.... Yeah