The woods gradually fade as the path narrows and becomes more rocky. You hear noises from the cliffs above you as small inhuman creatures emerge, chittering gleefully at you. More appear on the trail on both sides of you, emerging from hiding places. They approach slowly, evaluating their prey and searching for fear on your faces to savor.
A large group of Nibelung ambush the PCs on a rocky mountain trail, above a dense forest that awaits at the end of a steep slope.
A mountain trail (3) with a cliff leading up to the west (4) and down to the east (2). Farther east the slope drops farther to a dense wooded area (0).
The numbers in the map represent each section and show the relative section heights to each other; so, the border between a 3 and a 4 is Height 1 Up from the 3 to the 4. Draw the map in this manner instead of numbering the sections, with appropriate lines for cliff edges and such. It'll make it easier for players to tell what's going on.
The west cliffs (3-4) and eastmost cliffs (0-2) are the steepest, requiring Acrobatics vs. 1d6 to climb. The east slope (2-3) is gentler, requiring only Acrobatics vs. 1d4 to navigate (this may or may not be considered a climb; it's up to the moving entity to decide if they want it to).
The trail continues north and south in this manner for a longer distance if needed. Farther west, the cliff drops off from 4 to 3, then from 3 to 0. On the east, a dense forest thicket prevents movement beyond the 0s pictured (but those sections connect to each other across the row, unlike the other rows shown).
Sections have up to 6 borders each – the two to the west, the two to the east, and the one immediately north or south.
4 4 4 4 4 3 3 3 3 N -> 2 2 P 2 2 O O O O
The nyblings aren't the smartest creatures, but their tactics should still be better than those of wild animals. Tossers will reliably aim for incanting PCs and those with light armor, while the Scrappers try to use their Resilience debuff to make well-armored PCs feel some pain. The Caller tries to avoid its allies with Thunder Call, but it'll hit a Scrapper if it can hit two PCs at the same time.
The PCs overcome the ambush; Nibelung are either slain or forced to flee. The Caller is capable of some broken speech, so you may permit the PCs to capture and interrogate it. The PCs can find a Valuable or two among bodies or dropped bags.
The PCs are forced to flee. They get away, but not before taking some rough hits, suffering 1 Injury each. The direction of retreat may be dicated by positions at the end of the scenario; if one side of the trail is free, that's where the PCs escape to. If they're still surrounded, they may have to flee down the slope and into the woods; in this case, the Injuries may well be sustained from falls and painful rolls on the rocks. The dense forest is tough to navigate, but it also keeps the Nibelung at bay. Perhaps that's because something even worse lurks within?
This scenario becomes much harder in the darkness. Normally that should only happen at night, but you could easily convert this scenario into a cave tunnel (just swap the dense forest for the cave wall on the east side).
If you have enough PCs for a Caller to be involved, consider having the ambush occur during a rainstorm. This will reduce Acrobatics rolls for climbing and bestow Lightning Weakness, considerably shifting things in the Nibelungs' favor. Make it even worse by having the storm severely darken the skies and limit vision; torches and other fire-based light sources don't work, and the battlefield becomes shadowy.
If you want a bandit ambush, use Rookie Sharpshooters and Rookie Guards. For low PC counts you could use Agitated Farmers and Gangsters instead, though you might swap their Weapons for something more thematic (such as Shepherd's Slings, Bullet Crossbows, Cudgels, and/or Tabars). With any of these, use judicious renaming when conveying the Adversary to your players.