Two Heads are Better than One

Of the overland encounters, the one that intrigues me the most (of those mentioned) is the ettin ambush on the scree-filled mountainside. This presents an interesting opportunity. Ettins are CR4, which shouldn't be a huge challenge for characters of this party's level. The difficulty of the terrain will be a good equalizer, but the strength of an ettin lies in their two damaging melee attacks.
Moving along the road is treacherous, but not especially difficult. The road runs fairly level across much of this ridge, eventually running down to the valley floor in a series of switchbacks. At this point, though, it is generally flat. What makes it treacherous is the dry, loose footing and the narrow track.
Much of the morning has been spent picking your way across the ridge, being careful not to slip down the seven hundred foot fall to the base of the rocks. Unfortunately, there has been a recent rockslide from somewhere higher up the hillside that has sent a pile of loose rocks skittering down across the roadway before you. Investigating the slide, you can see no safe way to get across the slide without clearing the road. This leaves you exposed and in danger of causing further slides from shifting the rocks.
High on the slope above, three ettins have emerged from their caves to watch the party's progress across the ridge. In a rare moment of consent, they all agreed to dislodge a few good-sized boulders which caused the hillside to cascade down and block the road. Perception DC25 to notice the ettins above, unless the characters actively look for something of that nature, in which case either drop the DC to 18, or give them advantage. I think if they have Survival as a skill, they should get advantage. If they actively look, lower the DC.
While the PCs work to clear the roadway, the ettins will shower them with rocks from above. They can be targeted in return from distance, or someone could attempt to climb up to them. From your vantage point, you can see that the ettins are near the upper limit of the slope. Above them, the cliffside is still intacts, and you can see several caves opening into them. The ettins are about 150 feet above the road. Climbing the hillside is difficult terrain, meaning all movement is halved. At the end of each move, the PCs need to make an Athletics DC18 saving throw to keep their footing. If they fail, they fall prone. If they fail by greater than 5, they slide down the hill 10 feet.
Once anyone starts to climb the slippery slope, two of the ettins will start down to battle them. They are more sure footed in this terrain out of familiarity, but more reckless about their descent, also. They can move down the slope in two turns, but have to make the same Athletics ST. The extra movement doesn't count as extra movement for them, allowing them to take an action on their turn as well. If they fail their ST, they can "ride the slide" for the extra 10 feet and not fall prone. They are eager to join the fight.
Once they are defeated, their caves can be searched for treasure. Among the discarded bones and scraps of armor scavenged from previous victims, there are a number of usable items still to be found. I'll have to figure out what at another time.

Lake Encounter

Time to revisit the lake for an encounter with lizardfolk.
The lizardfolk have set an ambush. The drawback to the lake crossing for the weekly barge is the predictability of its schedule. There is almost always an encounter during the journey, which led the bargemen to build up a series of sandbars and start fortifying them into a semi-permanent site. They have gathered up loose shale from the western shore to fit together into a series of walls and a small shelter.
They built two arches crossing a gap between two larger sandbars, offering a protected inner harbor and connection between islands. They have enclosed a small area for protection from the elements and night attackers.
The end plan is to fill in more of the gaps between islands and encircle the center with a complete wall. It is a work in progress. The lizardfolk have chosen this crossing to set an ambush. They have gotten to the fort early, with three inside the building, and five others hiding in the water around the islands. There is a shaman inside the hut. They will wait for the barge to be anchored and people to start offloading onto the land. The lizardfolk usually target the shipment, but tonight they plan to target the people.
The lizardfolk hiding in the water will slip around underwater to get behind the party and bargemen. If the encounter needs to be ramped up, more can be added. Another shaman would make a good challenge, as would a king/queen or several more lizardfolk. Individually, they are not overly strong, but they have multiple attacks, and are good for swarming. Since they can breathe underwater for 15 minutes, it is always possible to have more swim in from whatever direction you feel they should. Another good option is to find creatures like crocodiles that can be used as companions.

One if by land

The overland route is fraught with its own perils. The journey itself can be made in three days at full speed when the road is in good condition. Unfortunately, the road is seldom in pristine condition. The steep slopes and loose rock often cause blockage and erosion of the roadway, which can slow down travel time, not to mention weather conditions or ambush.
Generally, the added concerns only force a fourth day onto the trip, although extreme conditions can add more. The road up out of Chance is a slow and difficult climb, with many steep inclines. The positive part of this is that the town is built at the base of a particularly large peak, and the road makes a long, mostly straight climb around a spur of the mountain. After 12 miles, the road begins switching back and forth as it crosses steeper sections.
Eventually, the road drops down slightly into a high valley between this mountain and the next. There is a road running through this pass deeper into the mountains toward mines in the distance. The next ridge is much rougher and made of particularly loose gravel. The next third of the journey is arduous and slow, crossing high on the ridge, with a lot of loose, slide-prone rock above and below. This is a prime spot for ambushes due to its isolation and the vulnerability of exposure on the hillside. There are caves high along the slope where ettins like to dwell.
The last third of the journey features another road leading into the mountains east of this bowl to more mines. This road is fairly well traveled, since there are 2-3 large mines that send iron and silver down into the town of Aronsburg. The road is better kept, and quickly drops down into gentler slopes, where it runs through forested slopes and past the occasional farm. This also is prime country for banditry, with so many places to hide and disappear into the wilderness. It doesn't hurt that the road often sees well stocked wagons being carried up to the mines with food and other provisional supplies, or back with full coffers of ore straining the boards of the wagons holding it.
There are patrols that move through this area, nominally "protecting" travelers and tradesmen, although many of these tend to be mercenary, and barely less dangerous than outright bandits.
Shelter on the first and final third of the road is easy to find, although the protection it can provide tends to vary widely. The middle section is exposed, and not a good place to rest or find any shelter. Most travelers try to rest before and after crossing it, opting for long marches to try covering the distance in one day. This is countered by the condition of the road itself, and the malicious intent of the ettins above who look for such actions and intervene.

Along the Cliffside

This is a brief entry. I still want to develop the last encounter, but I feel like it needs a map and some numbers for monsters. Today wasn't the day for that, so I'd like to consider some other elements that would make this area interesting.
The hillside west of the lake is meant to be too steep to traverse. There are cliffs here, but they don't rise directly out of the water. The cliffs rise several hundred feet up the hillside from the lake. The danger here is falling rocks. The rock face of the cliffs is shale, and the base of the cliffs are steep, shifting piles of loose rock. Movement across the scree would be difficult terrain and require an athletics check each round to avoid falling or shifting the rock. The DC would be high, 25 to cross without incident, missing by greater than 5 would create a rockslide that would do 4d6 damage while moving you 30 feet downhill toward the water.
Attempting to scale the cliff would be difficult and dangerous as well, since the loose rock will not easily accept climbing gear such as picks and pitons. They are as likely to dislodge more rock as hold for passage. DC20 athletics check to climb with disadvantage. Failure means no movement or 2d6 damage from falling rock on a fail of 10 or more.
Stone Giants love these rocky walls, and can easily move up and down them without delay. They live in the higher ridges above the cliffs, and use this as a pathway down to the lake. There is a 1 in 6 chance of encountering 1-4 stone giants for each day on the lake. Often they can be seen wading or bathing in the waters at the base of the rockslide, though sometimes their mood is more playful, and they will stand high on the hillside and throw rocks at the barge as it passes.
The fort on the sandbar that is near the middle of the lake is closer to the cliff face than the swamp. No one feels safe near the swamp, and since it juts out near the middle of the passage, the bargemen have been forced to find a defensible resting spot closer to the cliffs. The giants like to gather at the top of the ridge and toss rocks down at the lights and voices coming up from the campsite.
The good news is that with every trip across the lake, there is more stone available to build up the fortification. At this point, there is a four foot high wall that encloses the area around the dock. They have even begun building a wall out into the water to serve as a breakwater or eventually to enclose the barge and dock within the stone walls. There is no shortage of material in this area.
There is a struggle against the shifting sands of the sandbar. It is difficult to build up since the weight of the stone causes it to settle more quickly. The currents (from the main river and a series of small streams that seem to drain out of the swamp in this region) also cause the sandbars to shift and make permanent building a difficult task.

Which Way?

This is difficult to prep for. There are very different encounters to develop depending on how the party decides to move ahead in their quest. I think that means we're going to be doing some roundy-roundy here, in order to cover all bases. There need to be four points covered, the conditions and elements of the journey by land and sea, and a sample encounter of each.
I'm starting with the lake. The barge makes a weekly trip from Chance to Aronsburg and back. The lake is about 20 miles from town to town, and the barge takes two full days to make the crossing each way, with a day layover for loading and unloading. The barge stays in Aronsburg an extra day on Sundays, leaving for Chance every Monday morning. Due to the shallow depths in many places, the barge is poled much of the way by a crew of six who work in two person shifts. The barge stops about half way across the lake. The towns shored up a sandbar near the middle of the lake that can be used as an anchor point and fortification against attack. Generally, the crew remain on the barge, but the fortification is there if needed. This part of the journey is the most dangerous. The threat of attack in the night by lizard folk from the marsh is almost guaranteed.
It has almost become ritual, with the barge anchoring, watch being set, an attack made from some direction, and the monsters repelled. The lizard folk seem to be interested in grabbing food and small trinkets, so the boatmen often leave a crate or two of food and odds and ends near the edge for easy picking. The fights are almost choreographed to allow them to take the food and go.
Now and again, there is more to the fights. On this occasion, the lizard folk have gotten to the island first, and set an ambush for the barge when it arrives. There are many lizard folk surrounding the area, waiting for a sign to attack.

Chance to Aronburg

This is a dangerous area. The route from Chance to Aronburg by boat crosses miles of exposed water that is threatened by a mix of swamp pirates and lizard folk. The depths can be challenging, as the lake is broad and shallow in several places. This isn't really a problem in terms of traversing the lake, but the careful navigation required is a significant time delay during the crossing.
Another danger are the spiny rock formations that run out into the lake from the steep western slope that runs down into the lake. This forces traffic to the east, which also puts it within easy contact of the swamps and marshlands of the eastern shore.
These swamps are home to lizard folk, and trolls further east. They are also full of many other kinds of similar monsters, including shambling mounds. There are also more mundane creatures based in the myriad waterways that feed and drain the swamplands. There are swamp pirates that hide deep within these swamps, coming out to prey on anything moving across the lake. They occasionally make raids on Chance or the roads in and out of that town, disappearing back into the swamp for cover.
The road around the area sweeps wide of the valley, rising along a steep ridge toward the eastern mountains, with trails running further up into the hills and to the mountains further east, where there are numerous mines. The road rides along the edge of a scree filled slope that runs down to the valley below. Much of the area within the arc of roadway is low and marshy much of the year. The dark green area of the map defines the swamp, but the marshy lowlands stretch well east of that.
This part of the trail is prone to attack from bandit gangs that live in caves higher up the hills. These bands are a wild mix of human, orc, lizard folk and many other humanoid creatures united by the opportunity to raid. A common attack involves ambush, with avalanches started and then the attackers descend. They may roll rocks onto the travelers, or try to block their movement ahead or back.
And let's face it... there are probably giants in this part of the world. Certainly stone giants and likely frost giants as well.

Chance Meetings

The next morning the party can continue their journey upriver on a return boat headed for Chance, a small town located at the mouth of a small lake formed by a bulge in the river near a tributary river flowing into the Flushing from the east. With the flat plain in this area, the merging of the rivers caused the formation of a long lake nearly five miles long. Stretching to nearly two miles in places, the edges are protected by a ring of trees that hug the edges of the lake.
The boat takes you upriver into the town at the northern edge of the lake and the town of Chance. From here, the party will need to either charter some kind of transportation to continue upriver across the lake, or wait for a weekly barge that travels from one end of the lake to the other carrying large volumes of supplies and trade goods.
There is a much larger town on the southern edge of the lake where the river connects to Aron's Bowl. That town is pretty much the northern outpost of the settled area at the base of Deadfall, the cliffs dropping from the Upper Valley to the Lower Valley. This area is where the greatest growth has taken place in the last few years, with the rough, territorial lawlessness of the Upper Valley giving way to the organization of small farming communities scattered along the river and spreading back from it toward the mountains in the distance.
The farming valley spreads about 50 miles from Deadfall to the head of the lake, where Krithik River rushes down from the east. This forms something of a boundary with the wilderness. The river is a quick moving torrent that tumbles down out of the high eastern peaks, cutting across the plain in a fairly direct path to the Flushing River. East of the lake, the land is low, and frequently floods, particularly in the spring-time. With the swell of spring melt, the lake nearly doubles in width, mostly to the east as it overflows its banks. The rest of the year, the area is marshy and swampy until late August into September, when the dryness of high summer finally dries the land out and pinches the lake down to barely river width.
There is no western road, as the western mountains rise sharply from the riverbank. The road east swings wide around the swamps, running 40-50 miles out from the river to cut south along the foot of the eastern mountains. It also is an extremely dangerous stretch of roadway, cutting through wild, rough forests and across barren stretches of exposed ridge, covered in loose scree.
Trade in and out of Aron's Bowl therefore mostly travels across the lake. The lake is unfortunately fairly shallow, making it difficult to navigate at times. Hence, a weekly barge and mercenary boatmen. All of which can be found in the town of Chance at the northern edge of the lake.