Prime ability: Intelligence or Dexterity. A dungeoneer is (usually) a former adventuring thief who has lots of (painful, nightmare-inducing) experiences from tombs, dungeons, and other locations. She has survived more traps, falls, diseases, and poisonings that most adventurers will encounter in a lifetime.

Party Boon at Dungeoneer 1: A Dungeoneer has a preternatural sixth sense about traps, waiting assassins, imminent ambushes, and environmental hazards that goes even beyond her normal five senses. As long as she hasn't expended the last of her daily Heroic Deeds dice, the Dungeoneer can — if afforded the opportunity by other party members — correctly intuit the presence of a trap, mundane or magical, with 90% accuracy (roll separately for individual traps and other hazards). This 90% chance does not apply to attempts to disarm or bypass such traps.

Personal Boon at Dungeoneer 3: At third level the Dungeoneer may add her Dungeoneer levels to ability checks related to navigating, surviving, mapping, and becalming a dungeon, and receives Advantage on any passive checks (Listening, Noticing) and on saving throws related to dungeon environmental conditions, traps, and other hazards. The first two times on a given journey, dungeon delve, etc. that she must Defy Death due to traps or conditions mundane or magical, she may roll d4 dice, where normally the second occasion moves to d6 dice.

At Dungeoneer 2, the character is so familiar with dungeons and subterranean environs that he cannot become lost. This doesn't mean he knows how to proceed forward at every point — only that he is able to accurately retrace his steps back to their pre-dungeon origin.

A Dungeoneer, upon attaining 5th level, not only adds her level to dungeon ability checks and receives Advantage as noted for level 3, but also develops Tremorsense to a range of 120 feet when in dungeon environs. A creature with Tremorsense is sensitive to vibrations in the ground and can automatically pinpoint the location of anything that is in contact with the ground. If the Dungeoneer did not already possess darkvision, it gains it to a range of 60 ft when in dungeon environs. If it already possessed darkvision, the range is extended another 60 feet.

The Dungeoneer subclass does not go above Level 5.