The Tunnel Fighter is a fighter who has trained to combat creatures of the Underdark in their home. Most adept at fighting hordes of smaller creatures like goblins or kobolds, they can still hold their own against larger threats.

 

This was inspired by the eponymous Goblin Slayer from the anime of the same name.

Tunnel Fighting

Beginning when you choose this archetype at 3rd level you are adept at fighting in cramped quarters using gear carefully selected for the job. While wearing light, medium, or no armor and wielding only one-handed melee weapons or ranged weapons without the heavy property, you may tunnel fight, granting you the following bonuses:

• You may add your proficiency bonus to damage rolls with weapon attacks.
• You do not suffer penalties for squeezing through a space one size smaller than you.

You may use a shield and still gain these benefits.

Improvised Trapsmith

Starting at 7th level, you gain proficiency in the Survival skill and your proficiency bonus is doubled for any ability check you make that uses it. You may use the Survival skill to create makeshift traps.

Creating a trap takes an action. You may cover two adjacent 5 foot squares with your trap and after the trap is triggered it is destroyed. The Perception DC to detect the trap is equal to 8 + twice your proficiency bonus + your Wisdom modifier. It counts as difficult terrain to avoid the trap without triggering it if a creature is aware of the trap. It has one of the following effects when triggered:

• Bell: All creatures within 30 feet know the location of the triggering creature.
• Net: Restrained as per the Net weapon.
• Poison Needle: Poisoned for 1 round.
• Spike: Takes 1d8 damage
• Tripwire: Knocked prone

You can use this feature three times, and you regain all expended uses of it when you finish a long rest.

Improved Tunnel Fighting

Beginning at 10th level, while you are tunnel fighting, you have advantage on the first attack you make each turn.

Blindsense

At 15th level, your combat training and intuition reveals the location of any hidden or invisible creatures near you. You have blindsight 10 feet. If you already have blindsight, it increases by 5 feet.

Master Tunnel Fighter

Upon reaching 18th level, you have mastered close quarters combat. When you are tunnel fighting, creatures provoke opportunity attacks from you if they move within 5 feet of you. If you hit with an opportunity attack triggered in this way, it deals double the damage it normally would.