The party is ambushed by a Nibelung defense gang at the entrance to a dungeon. You can use it for ruins, ancient temples, castles and keeps, or caverns, and you could put it at a chokepoint instead of the entrance if you wish. Descriptions here assume the entrance of a castle keep; adjust the details as needed.
The first room of the keep is a foyer or waiting area of sorts for those awaiting an audience or here for other official matters. A single stone corridor leads farther inward, lit by burning wall sconces. Decorative curtains hang between them, a safe distance from the flickering flames.
This area is also designed to thwart invaders. Hidden behind several of the curtains are platforms of various elevation, accessed from deeper within the keep. Once one or more PCs advance through the hallway, the ambush is sprung. Adjust as needed if the PCs try anything unusual (permit them to do anything sensible given their Roles and Gear); otherwise, read the following:
Suddenly, the gates slam shut behind you, and several of the curtains fall away. The sconces fail to fully reveal what's in the shadows behind the curtains, but you hear inhuman screeching and the sound of claws on stone.
There's a sturdy locked door on the north end of the hall and two large, closed gates on the west end (the more open foyer area). Additional locked doors await at the end of the narrow elevated halls. None of these doors can be open within the context of combat's timespan, so no escaping. As such, this is a battle to the death; defeated PCs can spend 1 Karma at the start of their turns to regain 1/3 of their max HP, rounded up (and can take their full turn).
Elevated passages on the sides of the hallway each connect to a single floor section and not to each other. They are Height 1 up; climbing up or down is Acrobatics vs. 1d6, though note that all Nibelung Adversaries can freely cross Height 1 borders (including via Scurry). Any entity on a platform gains +1 level to Miss dice against ranged attacks made from the ground floor from height advantage (along with any Shadowy penalties on the attacker's Hit). Tiny crawlspaces connect the trap halls at the back ends; only the Nibelung can fit through them.
PC positioning depends on their actions taken prior to the scenario start. Tossers & Caller begin 1 back in halls, with melee 1 forward, scattered roughly evenly. High Tossers are able to throw around corners to hit PCs anywhere in the hall (but can't reach the foyer sections).
The hallway and foyer (0) are lit. The trap halls (1) are shadowy. The halls are narrow and do not connect in the west-east direction, and each borders only a single hallway section; however, occupying entities can throw or shoot around the corners to hit targets anywhere in the hallway.
1 1 O 1 1 O O O N-> O 1 1 1 1
Toss a fallen curtain over an enemy; this is melee (these curtains are heavy) with Hit: 1d8, Special: The target suffers -1 Power, Resilience, and Skill and can't see anything until it spends a Move to remove the curtain. Setting the curtain ablaze causes Damage: 1d6 (Piercing 1) Fire.
Melee Nibelung advance forward and engage any PCs that come to meet them. If the PCs try to avoid them, they'll go after vulnerable ranged PCs.
Ranged nyblings stay in the trap halls. They have nowhere to run and thus fight fiercely to the death. If they are unable to perform ranged Actions due to a PC present, give them the Scrapper's melee Action with all dice levels reduced by 1 and no Special entry.
The PCs overcome the ambush and may proceed or retreat as they wish. They may find some rewards, such as a couple Valuables or Wealth, depending on your player count.
The PCs are killed, ending the adventure. If you want this to be a low-stakes battle, let them crash through the doors and flee for their lives, suffering an Injury each in the process.
You may want to give the PCs a chance to avoid a battle to the death; an information-gathering interaction scenario earlier in the adventure might inform them of an alternate route or warn them of the potential of being locked in so they can act to prevent it. Alternatively, you might hide such clues in a preceding exploration scenario. Finally, you could rely on narrative hints and see if the players adjust their approach when entering the room.
You can include other Nibelung instead, such as Chargers or a Champion. You could even turn this into a level 2 boss fight with a Nibelung Assassin, but you'll want to make the map a bit more interesting for the Assassin's abilities. Consider having the sconces go out (plunging the map into darkness). Permit Acrobatics vs. 1d8 to leap from one trap hall to the one directly across, bypassing climbing down into the main hallway and back up (failure results in falling into the hallway, suffering Height 1 falling damage). This will give your Assassin plenty of maneuverability and increase the potency of its Skill-affecting plays.