The adventurers found themselves in the final throes of a massive battle on a bridge leading to a treasure cave. King Grol, the hobgoblin leader, barked nervous orders from a distance as his forces, including bugbears and goblins, were systematically cut down by the party. Bjorn, in his giant form, performed a spectacular leg sweep, knocking multiple bugbears prone and allowing him to rejoin his companions. As the fight dwindled, King Grol taunted Nissa about a love potion before making his escape, vowing to see her again.

After the dust settled, the party took a short rest. They harvested materials from the fallen foes and discovered a trove of loot, including several potions and a spell scroll. Bjorn claimed a particularly large and menacing great axe from a fallen ogre, decorated with skulls. Clara identified it as a magical weapon, and Bjorn spent the rest period attuning to it. Gundren Rockseeker, whom they were sent to rescue, finally emerged, claiming he was covering the rear during the fight. With the bridge secured, the group pressed onward.

The party soon found the entrance to Wave Echo Cave. The passage was a tight squeeze, forcing Bjorn to shrink and Avalanche to remain outside. Inside, the cave opened into a large cavern where they discovered the body of a dwarf, whom Gundren identified as his brother, Tharden. He had been killed by what looked like a spider. Grieving, Gundren gave his brother's magical Cloak of Protection to Nissa. Further in, they found a pit with a strange, alien-like goblin corpse at the bottom, its head oblong and its veins a sickly green. The party descended a rope into the lower levels.

Exploring a new cavern filled with the ancient skeletons of dwarves and orcs, the group was ambushed by massive, burrowing beetles. During the fight, Bjorn was struck by one of the beetles. The cursed axe he had attuned to took hold, sending him into a murderous rage where he could not distinguish friend from foe. He struck Breith before Clara managed to incapacitate him with a sleep spell. The party finished off the remaining beetles, and Breith carefully woke Bjorn by dealing a small amount of damage with his spiritual weapon. Realizing the axe was cursed and would trigger the rage anytime he took damage, the party decided to retreat from the cave.

They traveled back to Phandalin, where Sister Garaele performed a ritual to remove the curse, destroying the axe in the process. While resting at the inn, they met Gwen, a scholar and childhood resident of Phandalin, who was investigating strange mutations in the area—cows with tentacles and dogs with extra eyes—and believed the cause was connected to the cave. After a long rest, the party, accompanied by Gundren, returned to Wave Echo Cave. They cautiously entered a room filled with what they thought were ancient corpses, only for them to rise as zombies, including two massive ogre zombies. The party strategically retreated to the doorway, creating a bottleneck to fight the undead horde one by one.