Beyond the wall
Where We're Going We Don't Need Roads ... or trails or features that match any previous maps. If there were roads, they are now are indistinguishable from the surrounding terrain. No aids or boons to navigation checks.
Hyphae Don't Go Without Me! A thread-thin trail of hyphe follows the PCs, connecting the dots of their foot prints. It will follow over any surface, pebble, rock, ice, carpet, right up to running water. This may be followed by friends or others.
Come Again? Acoustic dampening substrate. The ground so soft and absorbs sound +1 boon to stealth.
Don't Call the Worms Running or stomping stirs up a Spore Veil: vision suffers -1 to hit (vision); stealth + 1 (but may attract fungal fellows... or others).
What'd You Call Me? (Duration 1 week then fades in 24 hours), speakers who have walked the same ground within a day of each other can speak to each other, and their voices can travel along the web of hyphae like a two-way radio (at any volume).
Dehydration Vacation All natural water sources have been used. Each PC must drink 2× water rations each day. Water magic is absorbed by the environment - however this spawns water mushrooms instead.
It's Learning! All spells fizzle, but grow 1d4 copies of spells in magic mushrooms (1d6 mins). Magic mushrooms function as per standard rules (store spell slot, dehydrate after 1 day, require water to activate)
Corpse bloom Any corpse left in the trail of the wall sprouts glowing growths. Use wandering monster table to identify a corpse. Each day, a Lichenbound Wandering Monster is spotted (1 HP, mindless, obsessive searching for water or organic matter. Spits spores if touched). Humanoids may have fragmented memories, possibly carrying water, spell remnants or magic mushrooms.
Dawn of the Dessicated
1d8 unearthed things (roll on entry and 1 day of travel)
1-2: Unsunk ruin covered in lichen. May collapse in 1d4 days. May hold mummified or Lichenbound monsters.
3: Unfun field of reanimated corpses (2d6 x party size) Lichenbound in ancient or alien synthetic clothing, partially cryo-preserved. Slow. Guarding a pool of clean water or something lost.
4-5: megalith stack (3D6+3 stones per party member) Each stone weighs as much as the party combined: covered in lichen, glowing. Skin-to-stone contact gives instant insight into the structures and plant life touching the adjacent hexes (+1 hex radius from the stone). If more than one player touches the stones simultaneously, they may use telepathy on each other. Must roll for madness or equivalent save to prevent stress or intelligence damage. Behaves like a stationary Sun Seeking Wall, and becomes mobile if all players touch a part of the megalith stack simultaneously. If dark, it retains other features but glows only. . . unless all players touch the stone simultaneously, the rocks awaken and move 5 ft per round to form a new Sun Seeking Wall - even at night. They will proceed north in any case.
6-7-8 A Fungal Fissure A chasm was carved as deep as the passing Sun Seeking Wall is tall. Look down and see a stream of clean water trickling at the bottom. That water is safe to drink, but protected, possibly.