I like the idea and where it's going, however I can see some things which I would tweak:
Its proficiency modifier seems off. At level 12 it should normally have a +4 (which it does for the saves and tentacle escape DC), however the attacks and perception seem to have been entered using +3 instead.
You may want to buff the strength a little as 17 isn't that high. The other Kraken creatures and the official CR 12 huge creatures tend to be comfortably above 20 most of the time. Something in the 20-24 range may be better depending on how hard you want it to hit.
It has no rules for escaping from the kraken once you get swallowed or what conditions are applied. Usually being swallowed by a creature would apply the restrained condition and have a set amount of damage to force the creature into making a Constitution saving throw or regurgitate the swallowed creatures. Otherwise they're just kind of there. Inside. Waiting. (EDIT) Forgot to mention some sort of damage to creatures inside as they get digested. Probably acid.
Its hit points feel a little low. The official Huge CR 12 creatures average about 190 hp so you may want to buff that a bit.
The confusing mist emits a cone which lingers. If it's just the Kraken exhaling it then you may find it easier to make it a sphere centered on the maw as it could be used defensibly. Lightly obscuring the area covered by the fog would also be thematically appropriate, or potentially imposing some sort of disadvantage on attacks of other creatures made in the area, or granting the kraken advantage against creatures within the cloud as their vision is affected but the kraken can see them fine when they're on the ground (via Tremorsense) or know where they are when grappled as they're in a tentacle.
Again - I'd like to emphasize that I like the monster, but I'd potentially change these things.
Please comment with any changes you would make. This is my first real crack at this with a monster I've always wanted to see.
https://www.dndbeyond.com/monsters/558537-cave-kraken
I like the idea and where it's going, however I can see some things which I would tweak:
Again - I'd like to emphasize that I like the monster, but I'd potentially change these things.
Please take a look at my homebrewed Spells, Magic Items, and Subclasses. Any feedback appreciated.
All excellent points. Thank you!!