This adventure path has been rolling along consistently in the design process: I think about where I need the story to be, look at monsters available for the chapter's level, list out 12 encounters in a variety of themes, write up the 1500 word (or so) adventure, then seed in the right amount of treasure for the level. Repeat over and over!

I knew I wanted to get back into the forest threats for the 7th level adventure, and I have my eye on that scrap of forest at the eastern edge of my map. I've already name-dropped that as the Skaldwood. For 7th through 9th level there are lots of forest-type threats: arboreal regents, animate plants, trolls, and so on. But I noticed a LOT of fire-themed monsters right in the middle there, about 8th level. So I decided I wanted my story to veer that way for one level, and then get back to that forest. So I think the 7th level is the "outer" Skaldwood, complete with corrupted arboreals, and 9th level will be the "inner" Skaldwood, which I think I'll call the Trollgnarl. In between, the heroes will hit a nearby mountain--a volcano, really--and fight the fire creatures that make such a good fit for that level. All they while they'll be following the trail of demons, and even finally get to fight a few.

I'm still kicking through the 9th level adventure, "Death in the Trollgnarl," but here are the 7th and 8th level adventures!

Chapter 7: The Skaldwood Regents (7th level)

At the end of the last adventure, the heroes learned that the arboreals of the Skaldwood have sworn their allegiance to a demon lord; if they don’t intend to check this out on their own, the scholar Gendal lets them know he’s heard that druids of the Circle of the Pruning Hook are the only ones who’ve been able to enter the Skaldwood freely. The arboreals there had always been peaceful, working to keep the trolls of the deep forest contained, but they’ve recently started attacking travelers. The arboreals of the Skaldwood are plainly part of the new, strange threat to the forests of the Northfells, and stopping them may provide further clues. The Skaldwood is in the eastern part of the Northfells, along the Steinvik River.

With only one exception, the arboreal monarchs of the Skaldwood have been corrupted by demons in service to Treereaver. The demons don’t remain with the arboreals, however (with one exception); they’ve either retreated to the deep, inner forest called the Trollgnarls or left for a nearby mountain to recover a magical cinder. The heroes are likely to hear about demonic activity in this adventure but not face any demons other than a frustrated vrock.

Part 1: The River Road

The road along the meandering Steinvik River has never been truly safe, but merchants and travelers the heroes meet on the way there tell them that no one survives the trip through the Skaldwood any longer.

Encounter 1a (Moderate 7)

The heroes come across an overturned wagon half-submerged in the Steinvik River. A beautiful woman cries for help before going under the surface of the water, but this is a ruse. She’s one of two evil naiad queens who want to lure travelers close to kill them. If the heroes don’t fall for this ruse, both naiad queens attack anyway. Goods scattered around the wagon include several bolts of fine cloth worth 90 gp in total, a moderate potion of swimming, and a greater shrinking potion.

Encounter 1b (Moderate 7)

Where the path through the Skaldwood starts to bend away from the Steinvik River stands a statue of a man nearly 20 feet tall. The statue holds a large bowl of water in one hand and a bowl filled with burning coals in the other. A naiad queen named Aytessia reclining in the bowl of water has awakened the statue with her primal magic, making it a giant animated statue. Aytessia directs the statue in a fight to defeat anyone who would penetrate deeper into the Skaldwood, but retreats to the river if badly wounded. The statue wears a large crown worth 360 gp.

Encounter 1c (Moderate 7)

Where the road becomes more of a muddy track, the heroes are attacked from beneath by two ankravs and an ankrav hive mother who tunnel up from an underground network they’ve dug. One of the ankravs still has an ornamental short sword wedged in its spine; it’s not useful as a weapon but is worth 200 gp.

Encounter 1d

After the ankravs are slain, a trapper named Ulf Nineskins pushes his way through the dirt out of the ankrav lair where he’d been left to die by the ankravs. Ulf thanks the heroes for coming along at just the right time. He openly admits to being a werebear who prefers to hunt in isolated forests. Ulf heard that people were staying away from the Skaldwood and thought to capitalize on the fur-bearing animals there, but it’s proved too dangerous even for him. He lets the heroes know about the arboreals of the Skaldwood follow four regents: the Spruce King, Lord Rowan, the Aspen Queen, and the Birch Monarch. Three of these—all but the aging Spruce King—has been corrupted by demonic forces. The Birch Monarch has gone one step further and commissioned trolls to defend their domain. Ulf gives direction to any of these domains the heroes wish. They can approach the following four parts of the adventure in whatever order they choose.

Part 2: The Spruce King’s Hill

The only arboreal regent who hasn’t capitulated to demonic forces is the Spruce King, an ancient spruce tree who inhabits a high hill. Reaching the paranoid regent isn’t easy, although he has good advice to offer.

Encounter 2a (Moderate 7)

Three awakened trees block the passage to the Spruce King’s hill. As their leader isn’t entertaining any visitors, they indiscriminately attack anyone approaching, no matter how peaceful their motives. If two are defeated, the last one flees to warn the Spruce King but falls victim to the vrock clearcutting around the Spruce King’s hill.

Encounter 2b (Moderate 7)

A vrock sent to corrupt the Spruce King has wholly failed to win his allegiance and is taking out his rage by destroying the trees that encircle the Spruce King’s hill. The vrock’s deadly spores weaken the trees and prevent Spruce King from awakening them. Once its evil work is done, it plans to kill the Spruce King himself. The vrock parlays with heroes who approach, offering them riches (which it doesn’t have) and information (which it doesn’t intend to give) if the heroes kill the Spruce King atop the hill. The fact that the vrock isn’t being genuine should be obvious and he probably ends up attacking the heroes out of frustration, fighting to the death.

Encounter 2c

The Spruce King atop the hill is grateful that the heroes killed the vrock he recently rejected, and even more grateful when he learns the damage the vrock was doing. He sadly expresses that his fellow regents have all been corrupted by a demon lord named Treereaver. Treereaver isn’t in this forest, but is working to extend his influence across the Northfells. The Spruce King promises the heroes a cache of treasure, including a greater animal staff and a lesser sturdy shield crafted from his own bark, if the heroes put the other three regents down.

Part 3: Lord Rowan’s Promontory

Lord Rowan controls the region of the Skaldwood along the Steinvik River.

Encounter 3a (Moderate 7)

Two awakened trees and an arboreal warden stand at the spit of land leading to Lord Rowan’s promontory. They are diligent guards and fight anyone who would approach Lord Rowan without his express invitation. The arboreal warden has a silver and platinum necklace worth 180 gp in its branches.

Encounter 3b (Moderate 7)

Lord Rowan, an arboreal regent, is always accompanied by two arboreal wardens. They are working to befoul the Steinvik River with casks of toxins provided by a demon envoy who is no longer present. Lord Rowan knows that it will poison river life and people who live downstream, but he’s convinced that doing so will allow the Skaldwood to grow larger and healthier. Unwilling to be confronted on this delusion, Lord Rowan fights anyone two tries to stop him or change his might, fighting until destroyed. The casks are mostly empty but contain a dose of nettleweed residue and a dose of malyass root paste.

Part 4: The Aspen Queen’s Grove

The Aspen Queen controls the largest swath of land in the south Skaldwood, where large stands of aspen trees grow. The aspen are all connected and mystically share information, both with each other and with the Aspen Queen in her sheltered grove.

Encounter 4a (Moderate 7)

When it’s clear the heroes have ventured into this part of the forest, the Aspen Queen sends four arboreal wardens to eliminate them. These arboreal wardens resemble the aspen trees so prevalent in the region and therefore use their Stealth skills to try to get a drop on the heroes.

Encounter 4b (Severe 7)

All aspen trees grow by germinating clones from shoots and suckers along its roots, and the Aspen Queen is no different. She’s been cultivating a successor in this grove for many years. Treereaver’s demons delivered primal secrets from Treereaver himself to expedite this growth, which the Aspen Queen eagerly accepted. But these primal secrets are corrupted and have infected both the Aspen Queen and her clone. Now, two arboreal regents—each a duplicate of the Aspen Queen—occupy this grove, but they are both visibly sickly and attack intruders in a rage. The arboreal regents are connected by pestilent strands of moss that prevent them from traveling more than 20 feet from each other. Cutting these strands doesn't hurt the regents, but allows them a bit more mobility. The Aspen Queen’s grove has a wand of heroism hanging from an ordinary aspen tree, affixed by a murderer’s knot.

Part 5: The Birch Monarch’s Dell

The demons considered the Birch Monarch the most important arboreal regent to corrupt, as they controlled the land around the Trollgnarl, the central region the demons consider the most important part of the Skaldwood. It is here the demons intend to create a mystical gate to allow Treereaver to step directly into the Skaldwood. But the Birch Monarch was already long ago corrupted by proximity to the Trollgnarl, making deals with troll witches and allowing voracious trolls free passage. This has proven the arboreal’s undoing, as a troll king recently killed the Birch Monarch and taken the arboreal’s wooden throne as his own.

Encounter 5a (Moderate 7)

The area around the Birch Monarch’s realm is patrolled by an unfortunate troll who does her best to keep two shamblers moving. The shamblers merely want to stop and wait for prey to come along, but the troll was ordered—under the threat of being eaten—to goad the shamblers into patrolling the region. The heroes likely hear the troll barking orders at the plants from a distance. All three of these foes fight any creatures they encounter. If the heroes defeat the shamblers first, the troll seizes her opportunity and flees the Skaldwood entirely.

Encounter 5b (Moderate 7)

Near the dell where the Birch Monarch keeps their court, four trolls are eagerly ripping several dead arboreals apart. The tree-people taste awful, however, so the trolls are eager for fresh meat and attack until slain. One of the trolls has most of a gnome it’s been snacking on; the gnome’s +1 resilient breastplate is still functional.

Encounter 5c (Severe 7)

A troll king lounges on an elaborate wooden throne at the center of the dell, its warty feet propped up on the dead body of the Birch Monarch. The troll king makes a big show of holding a court, and might even give polite heroes some clues about how the Birch Monarch got a little too comfortable with the nearby troll clans and paid for this carelessness with its life. Ultimately, though, the troll king’s appetite gets the better of him and he attacks the heroes. The throne has a two tree feather tokens hanging from it.

Conclusion

When the three evil arboreal regents are dead, the Spruce King provides the heroes with his promised reward. He’s also been able to question some of the nearby trees. The demons who came to the Skaldwood were planning to burn part of it with unholy fire and open a magical gate for Treereaver to come through. The Spruce King knows that many demons went to capture the unholy fire from the nearby mountain called Forgepeak, an extinct volcano that rises from the plains west of the Skaldwood. He suggests the heroes go there.

There’s a chance the heroes want to instead explore the Trollgnarl first, as it’s right here in the Skaldwood. You can allow them to do so, but they should be able to retreat if the dangers prove too much for them—they’ll get back to the Trollgnarl before too long.

Chapter 8: Forgepeak Fires (8th level)

The extinct volcano of Forgepeak was once the home of a clan of dwarves who were slaughtered by a red dragon named Zarvendishar generations ago. Yet Zarvendishar wants to awaken Forgepeak again and blanket the land in fire. To do this, she’s slowly cultivated a link to the lands where the Plane of Fire and Plane of Earth meet to recover a magical cinder suffused with primal power called the magma spark. Treereaver wants his demons to steal the magma spark and use it to burn a gate into the Skaldwood, but the crafty dragon already defeated the demon thieves.

Part 1: Outer Chambers

Forgepeak is a labyrinth of chambers around the volcano’s flanks. The outermost chambers are easy to spot from a distance at night, as they glow with firelight. Finding the entrances during the day requires a successful DC 24 Perception or Survival check. These chambers all connect to each other, but the inhabitants are so territorial that the connecting passages haven’t been used in years (or longer). The heroes can approach any of the locations in the first three encounters, but only the fire giant caves lead to the dwarven hearths in Part 2. The temperature throughout these chambers is severe heat (1d6 fire damage every hour).

Encounter 1a (Moderate 8)

Heroes approaching the mountain draw the attention of a chimera with a red dragon head and three flame drakes that follow in its hunts, fighting for scraps. Their cave contains the remains of past victims and a jade bauble.

Encounter 1b (Moderate 8)

One of the caverns that seems the least used is actually one of the most dangerous; a patient roper lurks among the stalagmites of cavern and attacks anyone who ventures near. This volcano-adapted roper has resistance to fire 10 and a weakness to cold 10. The roper’s treasure includes fifteen gems worth 15 gp each, a greater comprehension elixir, and a javelin of lightning.

The Encounter 1c (Moderate 8)

The largest cave is the home of a fire giant named Graxim who, along with his brother Arxim, was exiled from a distant fire giant clan for unsuccessfully attempting to overthrow the clan’s king. Graxim keeps an eye on the mountainside for likely targets. He starts combat by hurling rocks and then charges with his greatsword. If reduced to fewer than 30 Hit Points, he flees the mountainside for good.

Encounter 1d

The fire giants have a cave set aside as a storeroom. It contains several banners from their ill-fated overthrow attempt as well as a coffer with funds they had intended to use to bribe supporters before they were driven away. The coffer contains four emeralds worth 100 gp each and silver earring worth 25 gp.

Encounter 1e (Moderate 8)

The innermost of the three chambers claimed by the fire giant brothers is a combination of sleeping chamber and workshop; any hero Investigating this chamber discovers old dwarven ruins indicating this was once the entrance to a dwarven outpost. The fire giant Arxim works here, unwilling to go outside like his brother because of severe agoraphobia. Arxim nevertheless is a brutal bully who attempts to kill anyone entering his chamber. The worktable contains a necklace of fireballs type II. The back of this room holds the old iron door to the dwarven hearth deeper in the mountain, which the fire giants haven’t used.

Part 2: The Dwarven Hearths

The dwarves who once occupied these chambers are all long dead, killed by Zarvendishar long ago. The primal energies they used to keep their forges a consistent temperature have all run wild, creating several elemental creatures. The temperature here throughout this area is extreme heat (1d6 fire damage every 10 minutes).

Encounter 2a (Moderate 8)

The large forge chamber is now a playground for fire elementals. A fire wyrm and two living wildfires cavort in this area and are quick to attack any intruders.

Encounter 2b (Severe 8)

The largest forge is lit, but only because it now houses an elemental inferno that attacks the heroes. Upon defeating the elemental inferno, the heroes can find a red dragonslayer’s shield (which the dwarves created but never got the chance to use) and the sole passage from the dwarven forges to deeper into the volcano.

Encounter 2c (Moderate 8)

The stone-lined passage to the center of the mountain seems open, but it is trapped with a lava flume tube trap. When the heroes approach this trap, the passage closes in front of them, barring the way. The only way to move forward is to enter the lava flume tube (whether or not the heroes were able to disable it).

Part 3: Realm of the Stone Giants

Zarvendishar thinks she has nothing to fear from intruders blocked by the lava flume trap, as she believes the only opening to the heart of the mountain is closed. As the heroes will learn, she’s wrong. In the cold stone near the base of the extinct volcano, a tribe of stone giants labors to sculpt the rock and train their loyal beasts. These stone giants are initially hostile to intruders, but by strength of arms the heroes can win the respect of the tribe.

Encounter 3a (Moderate 8)

At the borders of the subterranean lands claimed by the stone giants, the heroes encounter two bulettes on patrol. These creatures are aggressive and fight to the death. Both bear a knot of crystals protruding from their flesh, like a brand made of quartz. Each of these strange stones can be removed from the bulettes’ skin and is worth 100 gp.

Encounter 3b (Moderate 8)

A stone giant and a triceratops march down the passage the heroes traverse and command the heroes turn around. As there’s not any way for the heroes to go that doesn’t involve leaving the mountain, they’re unlikely to do so; the pugnacious stone giant attacks, directing his triceratops to fight at his side. The triceratops has a quartz “brand” worth 100 gp, just like the bulettes.

Encounter 3c (Moderate 8)

In the larger chamber belonging to the stone giant clan, the heroes see over a dozen stone giants hunkering down in their small huts along with a variety of subterranean animals they keep (including giant lizards and cave bears). The stone giant thane insists that the giants will overwhelm and drive off the heroes with their numbers unless the heroes can defeat the tribe’s champion: an elite stone giant named Foshtran and his trained cave bear. If the heroes win, they have proved their honor and the stone giants become welcoming to them. The thane, Morovosh, asks what brings the heroes into the mountain. Morovosh knows that the red dragon Zarvendishar commands a powerful relic called the magma spark and that demons recently came to steal it. Whether the demons fought with Zarvendishar or allied with her, the giants don’t know; they try hard to avoid the arrogant and violent dragon. Morovosh knows where Zarvendishar lairs and shows the heroes the way through secret tunnels.

Part 4: Zarvendishar’s Lair

Forgepeak’s heart is exceptionally hot, and will be even hotter once Zarvendishar finally awakens the volcano with the magma spark. This area is incredible heat (4d6 fire damage every minute).

Encounter 4a (Moderate 8)

A magical laboratory created by Zarvendishar long ago is where she keeps the magma spark when she isn’t using it in the volcano’s core. Here, an efreeti smith and the efreeti’s two jann slaves work on the magma spark, constantly imbuing it with elemental energy. The jann surrender if the efreeti is killed, but they’re in a rough spot: the efreeti extended his fire immunity to them for as long as he lived, so the jann aren’t likely to live long in the incredible heat once the efreeti is slain. If the heroes arrange for the jann’s survival, they explain that several demons recently crept into these chambers looking for the magma spark, but Zarvendishar discovered and killed them. A wand of smoldering fireballs (3rd level) is here in the workshop; the efreeti has been tinkering with it.

Encounter 4b (Severe 8)

In the heart of the volcano lies a vast chamber where the elite adult red dragon Zarvendishar works to stoke the lava to greater fury with the magma spark and her own breath. She spends her time on a vast ledge overlooking the seething, fiery core of the volcano. She is weeks or months from completion, but nevertheless labors with an intense focus. She doesn’t suffer intrusion lightly and fights to drive the heroes away so she can finish her work. She gloats about what she’s doing and how she recently slaughtered “the other thieves” who came to take away her magma spark to the Trollgnarl, and she arrogantly insists she’ll kill the heroes as well. The magma spark is here; it’s a shard of solidified fire about a foot long that functions like a greater staff of fire.

Encounter 4c

A side chamber contains Zarvendishar’s hoard: 3,612 sp, an obsidian statuette of a dwarven woman worth 30 gp, a belt of the five kings, a young red dragon’s breath potion, a greater darkvision elixir, and a scroll of breath of life in a brass tube worth 20 gp. There are also the charred remains of two dead vrocks and a dead succubus, the remains of Treereaver’s forces who attempted to steal the magma spark from the dragon. The succubus has a scorched shoulder bag containing a leather map of the Skaldwood and the Trollgnarl at its center. An arrow from the symbol for Forgepeak to the Trollgnarl shows where the demons planned to take the magma spark once they retrieved it.

Conclusion

Whether through engaging with Zarvendishar or searching the dead succubus in Zarvendishar’s hoard, the heroes know the demons have designs on a region within Skaldwood called the Trollgnarl.