Overview

Generate an encounter for a level 6 party entering the Iron Caverns. I want environmental hazards — maybe some crystallized acid pools — and a mix of combat and exploration elements. The party has just lost their guide.

The cavern floor undulates with jagged crystal formations. Pools of shimmering viscous liquid reflect the dim glow of your lanterns — each pool radiates faint acid fumes. A narrow path winds between towering stalagmites, but one has recently been hacked down, blocking the way ahead.

Add a crystal spider variant — make it unique to this environment, not just a reskinned normal spider. Give it CR 4.

Geode Spider — Medium Monstrous Spider, Neutral Evil. AC 15 (crystalline carapace reflects ranged spell attacks — advantage on save vs. single-target spells). HP 72 (9d8+27). Speed 30ft, climb 40ft. The body is encrusted with razor-sharp crystal shards that refract light, making targeting difficult.

The party spotted an underground river beyond the acid pools. Generate what they might find if they follow it deeper.

The river emerges into a vast underground grotto — a cathedral of natural stone lit by bioluminescent fungi. On the far bank, you spot the remnants of a dwarf settlement: collapsed forge chimneys, half-submerged anvils, and — most disturbingly — a circle of standing stones etched with runes you recognize from the World Forge prophecies.

Generate an NPC — the survivor who still inhabits this ruin. Tie them to the standing stones and give them a reason to help the party find their missing guide.

Thrain Ironvein — Hill Dwarf Commoner, Neutral Good. The stones speak to me, the old dwarf croaks, tapping his knuckle against the rune-carved surface. They showed me your guide came this way, three suns ago. She was looking for the Deep Gate — the one that opens when the acid pools burn cold. I've been waiting for someone to find this place since the collapse.