AKA: Common Whale
Baleen whales are the titans of the ocean, making up some of the largest creatures on the planet. This category includes whales such as the humpback, the blue whale, the right whale, the fin whale, and other behemoths of the depths that filter-feed on small krill and plankton. They are saught out for valuable oil, blubber, bone, ambergris, and other body parts by sailors around the world, though harvesting these items is frequently quite dangerous.
The specifics of habitat, society, and behavior will vary depending on the specific subtype of whale, but they share many features in common.
Baleen whales are rarely faught except by predatory ships of humans -- their sheer size and speedy swimming are more than enough to kepe them safe from all but the boldest and most massive and monstrous of ocean predators. When they are faught, they rely on slapping with their fins and tail, and occasionally ramming. The damage they do is massive, on the level of seige engines, but their first response is usually to flee.
Baleen whales communicate for miles underwater with moaning songs. They travel in loose tribal groups called pods, and range over immense areas of open ocean, moving between blooms of plankton and krill, and mating and birthing areas that are shallower and safer.
A leviathan is one of the most immense creatures in the sea, growing up to 1,000 feet long, the size of entire beaches. It generates tsunamis with its movements, and can contain villages in air pockets in its gut. They mate in the arctic waters, attended by other whales. They are considered the high lords of the whales, and killing one of these ancient creatures is usually a cause for a massive ocean campaign against the murderers.