Out With the Old
Plane of Ooze
Optional Rule: Trackless Mud
The clinging ooze is difficult terrain; each foot of movement, walking or swimming, through the muck costs 2 feet of movement. Creatures adapted to muddy environments such as mud mephits and frogs ignore this restriction.
The Plane of Ooze is called The Swamp of Oblivion for a reason. Characters in the Plane of Ooze have disadvantage to Wisdom (Survival) and Wisdom (Nature) checks to find their way.
On the border of the Plane of Ooze, a vast forest stretches out into the Elemental Chaos, becoming a region known as the Plane of Wood.