The Kētos and Their Strange Ecologies

The Kētos

Some say that the Psári grow even too large for the islands, and they flee their deep channels in favor for the Deep. Here in the wide ocean they can grow into even greater monsters of the sea, the mythical Kētos.

Kētos are so large it is said they carry whole reefs on their backs as they slowly wander the world. They can trail miles of kelp behind them that is rooted in their thick hide, and that a mere flick of their massive fins could send any ship flying through the air and then into the depths. Only the foolish and the mad sail in the Deep, so these reports are rarely given credence.

Sometimes, the giants of the deep oceans wander into the shallow Sea around Ánemos. They are strange and deformed leviathans, often with whole ecological communities clinging to their bulk. They can only comfortably navigate the deepest channels, though in such shallow water they often get lost and irritable, they will likely lash out in fear and frustration...

Their Strange Ecologies

Kētos types (1d6):
1: Coral Reef: Coral has grown in the hide of the Kētos  and shelters many animals... Inhabitants will protect the Kētos if attacked, -10 ft of movement +2 AC

All of those little fish are going to come out and fight you

2: Kelp Forest: Kelp creates an entangling cloud slowing ships in 50 ft radius around Kētos, -10 ft of movement

3: Mollusc Armor: Mussels, oysters and clams armor the Kētos and make their tails more deadly, +4 AC and 10d8+12 bludgeoning damage with tail smash

Just ready to cutsmash the shit out of you

4: Mangrove Forest: A mangrove forest grows on this Kētos's back sharing sugars and proteins between them; cannot dive, heals 10 HP per round, -20 ft of movement

Like this, but rooted on the back of a massive fish

5: Sea grass prairie: A living green fur covers these Kētos, and grazing their backs are territorial dire dugongs. Dire dugongs will fight for their pastures.

But giant and sucking off your face

6: Merfolk nomad settlement: The merfolk have settled this Kētos, serving as both home and mount. They are the traders of the undersea world slowly plying the depths between merfolk settlements.

Thoughts

The Kētos is the like final form of the Psári, they should be really scary and more of an environment than a creature. It should also be really hard to kill them (unless of course you land on their backs, get in their ears and stab their brains or something, but who knows what weird creatures make their homes beneath the flesh of a leviathan?) They should be so tough and scary I am not even going to give you a stat block.

Think about the bad ass wizard who lives in a lair made of living trees in a mangrove forest on the back of a Kētos prowling the deep channels around the world, mind controlling his pet/island/home to steer. I wanna meet him.

If your players ever get a few ships and hire a large crew of competent harpooners it's conceivable that they could kill one traditionally. Boy oh boy, all that lard would fetch a hefty price...