The Shadowrealm AND a Giant Snake/Tentacle are hidden in the middle of the Sundial/Watch we use to change time (Pictures included)
That is my best guess of what this image depicts (See further down below for the hidden image), but essentially, in the middle of the sundial/watch we use to change the time of day there is a swirl which is akin to the runes in evergaols:
Evergaols seal things, they are prisons- They are a 'shadow pocket realm' in essence, which seems to me very reminiscent of the sealed shadow realm that Marika veiled. So I thought "wouldn't it be crazy if there was something underneath it- Like a shadowrealm".
Evergaol - You can faintly see the runes I am referring to - See the ripped texture below
Ripped texture of the pattern of runes under evergaols
Turns out there literally is (THIS is hidden UNDER the swirl in the middle of the sundial)
ORIGINAL UNALTERED HIDDEN IMAGE
HIDDEN IMAGE Under the \"Swirl\" - 1
HIDDEN IMAGE Under the \"Swirl\" - 2
It has a giant tail or tentacle that reminds me of several depictions including the beasts we used to find around the map, the tail on the creature of the banished knight outfit and the tail on the banished knight helmet (As well as maybe Eiglay or the Base serpent or the World Devouring Serpent etc)
Old Version of the Map with Monsters in the ocean (Zullie THE Witch)
And there are stars everywhere, which reminds me of the Nox and their false sky- Banished underground.
My full video including other elements of this secret and the watch itself can be found here: