Stone stairs descend into an underground passageway with high ceilings. Grotesque carvings perched atop ledges on the left and right scowl down at the party. Ahead, a pair of metal doors seals access to the ancient tomb.
Hidden among the carvings and nooks and crannies in this dark underground passageway are monstrous creatures ready to ambush any who would intrude on the sanctity of the tomb. Determine why these guardians are present based on the details of the tomb in your adventure. Perhaps they're here by happenstance, or they were placed into a magical stasis until the spell detects the presence of intruders.
A battle in such a tight passageway encourages use of section border blocking and area attacks. Light sources are essentially mandatory, but it's fairly easy to light most of the battlefield.
The lower passageway is flanked on each side by narrow ledges, Height 1 bordered from the walkway. The partially-crumbled stone walls can be climbed with Acrobatics vs. 1d8. Any entity that occupies a ledge section is Debilitated and Vulnerable due to the difficulty of moving around in such a cramped area.
The north exit is blocked by metal doors that will take longer to open than is practical within combat's short timeframe. The south end has a set of stairs that lead back outside. Entities atop the stairs can't see or otherwise affect entities within the passageway. If need be, draw sections outside based on the terrain of your adventure.
Combat begins as the monsters emerge from nooks in the passageway. They aren't clever enough to ambush with great effectiveness, so they enjoy no Initiative bonus or other benefit. If you're concerned about players spotting the ambush early, you could have the south enemies burst from the wall; while effective, you'll want to prepare a pretty good explanation for why monsters are waiting behind a wall. An alternative would be to have all the monsters start north of the players, though this will make the scenario considerably easier; in this case, you should have the Gargoyle start on a south ledge in stone form, perfectly blended in with the surrounding statues.
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The Gargoyle will use Flight and Springing Rake to fly down from the ledge, attack a PC, and fly back up to the other side. Whenever possible it will play Reactions from its hand to avoid being Grounded by Stone Form; however, it will play Stone Form instead of just taking the hit whenever the Reaction can help. It will attempt the same tactics even while Grounded, except it will rely on its high Acrobatics score to climb up and down. The Gargoyle will try to avoid any PC that climbs up and will focus its attacks on weaker ranged PCs. If you chose to have enemies appear north of the PCs, the Gargoyle will go after any PCs that look to be fleeing for the stairs.
The Gluttonmuck will neither strive for melee combat nor seek to avoid it. It will target as many PCs as possible with Corrosive Spray regardless of any friendly fire concerns. The Gargoyle is smart enough to try to avoid stopping in dangerous sections as a result of this. The Gluttonmuck will always choose its own section as a target if at least one PC is present, limiting the effective range to 1.
The Lode Spider is lumbering for its species, largely unable and entirely unwilling to climb to the ledges above. It will target as many PCs as possible with each Gravity Web; however, it's not smart enough to use this Action to its greatest potential (such as Hindering a lone PC Swashbuckler or Warrior that might seek to climb the ledge and lock down the Gargoyle). It is smart enough to avoid the Gluttonmuck's spray, though; although the spider is most effective upon entering melee, it will stay away from the Gluttonmuck and let foolish PCs charge in to meet it instead. If the Gluttonmuck seems likely to target its occupied section, the Lode Spider will advance one section south if that lets it attack a PC in melee. If the Gluttonmuck is defeated, it will advance as much as possible to reach ranged PCs that are likely interrupting its Incantations.
The Zombies attack PCs mindlessly, driven by their living flesh. They are not smart enough to avoid the Gluttonmuck's attacks (and probably won't last very long as a result).
Enemies on the south side will block section borders in order to prevent the PCs from escaping. If you choose not to have any enemies start south of the PCs, enemies other than the Gargoyle will move in to do this as soon as possible, though their low Initiative rolls means PCs are likely to get away. You might choose to have the enemies not follow, retreating back into nooks and other hiding places until the PCs return. If the PCs try something elaborate (and ridiculous), the enemies may retreat into the tomb to ambush the PCs at a different location later.
With the guardians defeated, the way into the tomb is open. If this is a side quest, you might run an exploration scenario for the tomb, filled with traps and treasures.
The PCs flee from the tomb's entrance; each suffers an Injury. If the battle was close, the PCs may return (after healing) to find the entrance now unguarded (or so lightly defended that running a scenario isn't needed). If the PCs were routed without much damage to the Adversaries, however, they're still there and will continue to defend the tomb. PCs will be wise to the ambush, however, and may gain a tactical advantage in the next attempt (such as better positioning, starting Gear, and other benefits).
This scenario fits equally well in caverns, canyons, rocky mountains, and similar environments. In such cases, the Gargoyle is likely hiding behind a rock formation as opposed to blending in with statues.
With five or more players, you might choose to run two Gargoyles for flavor. The Lode Spider, Gluttonmuck, and Zombies each make tactically interesting additions; you couldn't go wrong with any of these that you choose. Note that running two mini-bosses means you have to manage two decks and hands of cards, which might be taxing. Alternatively, if you don't want undead, you can easily swap the Zombies for another Gluttonmuck or Lode Spider.
Increase the difficulty by adding some sort of trap or other terrain hazard. Fire jets could be appropriate, as both the Gargoyle and the Lode Spider enjoy some resistance. Such a trap or terrain feature might fire at a certain section (or random ground floor section) at the end of every round as an Area Attack, or it could trigger upon crossing certain section borders. You could also allow the Gargoyle to ignore the penalties for fighting on the ledge; in this case it would be happy to engage most PCs that climb up, though a high-Defense Warrior could still be a problem if the Gargoyle lacks Piercing Actions in its hand.
If you want to make the darkness even more threatening, you could have the Gluttonmuck's Corrosive Spray douse any flame-based light sources that hit PCs are carrying. You might also rule that light sources on the ground level that illuminate adjacent sections only make the ledges shadowy as a result of the angles and the statues. This would make the Gargoyle more difficult to take down with reach and ranged attacks, though with its low Miss dice, a PC blind firing is still likely to hit. At best this limits the use of certain auto-hit implements like Orbs and Chimes.
Perhaps this tomb seals a great evil, and you want its protectors to reflect that. While you could reflavor the Adversaries as demonic creatures with few changes needed, there are a number of viable alternatives as well. You could exchange the Gargoyle for a Mandragora, which uses teleportation instead of flight to harass the PCs. The Lode Spider may be swapped for a Possessed Tome, or you could have a Sacrificial Altar that the Mandragora seeks to take advantage of. The Gluttonmuck could be swapped for additional Zombies, especially if you're at lower player counts and no Zombies are present, or you could include Resentful Spirits.
If the tomb is from a mechanical civilization (or are instead mechanist ruins), you could even swap out all the enemies for a pack of Clockwork Sentries that start both on the ledges and the floor. The sentries can't effectively move between them, so they should ignore any penalties for fighting on the ledge. The first round here can be extremely dangerous for PCs without good defensive options, though stout PCs like the Warrior can shrug off the sentries' weak attacks (unless unlucky Miss rolls from shields start piling on Fire Weakness from Viscous Spray).