Locked Away

The little halfling prepared herself. With her magic boots she could easily run past them, but what lay beyond? There were four undead that she could see, but could there be more?
The zombies shambled ever closer. There was a noise behind from the rock slide, but she dare not look. Just as the lead zombie was almost upon her, ..."Thunk"!
An arrow was now sticking out of the eye socket of the closest zombie. It dropped to the ground. A quick look behind her revealed Gildrid had squeezed himself halfway through the a hole between the top of the rockslide and the ceiling.
"Thanks, Skinny", Miss Adventure said before she sprinted behind the furthest undead. Slash! Her short sword dug into the creature. It swung around to face her as the rest took interest in Gildrid.
The elf was trying to squeeze himself through as the zombies moved closer.
He had let loose another arrow, but it went wide. Suddenly he slid forward and smashed into the floor. Nemon, the old mercenary, had shoved Gildrid the rest of the way through.
Gildrd, crumpled at the bottom of the pile of rocks, was set upon by the zombies.
He slashed furiously as they pummeled him with rusted cudgels.
One of the zombies dropped when a large chunk of rock crushed his head. Nemon was halfway through the hole using rocks as missiles. Meanwhile, Miss Adventure had finished her undead foe, and was working on another.
On the other side of the collapsed tunnel, Gustav and Mellon were digging out the remains of Gruffydd. Finally an ankle appeared. Mellion began to tug. Gustav grabbed the other leg. With one last effort they pulled the dwarf free. He groaned.
"Still alive!" Gustav yelled. He grabbed his holy talisman and began to pray.
Nemon, Miss Adventure and Gildrid dispatched the last zombie in time to see a strange glow come form the other side of the rockslide. "What's going on back there?" Nemon shouted.
The weak voice of Gustav responded, "He's alive, but he's going to have a headache".
The rock pile was cleared. Everyone rested. All but 2 vials of the Tears of Shehalla were drank. The zombies had yielded little in treasure. But they had guarded a stairway down.
At the bottom of said stairway was a chamber. It showed damage from a massive brawl. There was dried blood, broken weapons, gouges in the masonry, and strangest of all, long spikes embedded in the walls.
The was another stairway down, but the party's attention was drawn to door. It was boarded shut.