Sinking Bog

"Through the murk across the bog, you can just make out the silhouette of small stone shrine in the distance. Getting there without getting entirely submerged will require you to carefully pick your way across rotting wooden footpaths and increasingly wet squelching clumps of turf and swamp grass. Your footfalls, especially among the heavier armoured of you push the spongy ground deep below the waterline, above your ankle on occasion.  The smell of wet rot permeates throughout and every now and again you hear a dull splash, as if something big rolled over beneath the muck. You pause waiting for another sign of movement, but are only rewarded with the settling ripples and chirruping frogs."

A 6 staged 40x40 map featuring a small half sunken shrine in a sinking bog. The seventh staged map is just water with no land features, which could be used if you want to sink everything... or perhaps use it on the approach/escape in canoes. 

I used this map for a froghemoth den boss battle. 

Lair actions included:
1) Grasping weeds. Which cast entangle on an island. DC16 to escape.
2) Sinking islands. Which progressed the stage of the battle to the next map. Anyone caught by grasping weeds and whose island had sunk, was now underwater holding their breath and struggling against their bonds. If they wore heavy armour, disadvantage on the escape roll.
3) To the muddy bottom. If there is a character grappled by the froghemoth's tentacle, it plunges the character down to the bottom of the swamp, where the silt is so thick its almost mud. The tentacle tightens squeezing all the minutes of air out of the character, leaving them with only their CON bonus in rounds of air left. The character is also effectively blind in the lightless muddy bottom and anyone in heavy armour has disadvantage on the escape roll.

Optional puzzle mechanic
The sunken shrine's door could only be opened by depressing both eyes in the fallen statue's head. When pressed, water wells up from behind the stone eyeballs making it appear as if the statue is crying. The clue "TEARS OPEN THE WAY" can be found on the stone plinth in the south of the map... or anywhere you deem fit. 

The interior of the shrine is submerged under a couple of feet of water. There is a stone snake head with open mouth and fangs exposed in the Northern alcove. Put whatever McGuffin you desire in there. 

40x40 [4000x4000]
100px grid