Comments from the Thumb: Finally, the second piece in my Monster Hunter lineup! The concept is a straight-up high-damage tank-type build.
The fighter that doesn't adapt dies. This is an increasingly common opinion among adventurers of all backgrounds. The deeper an adventurer goes into wilderness and dungeons, the stronger the monsters he encounters will be. There comes a point where a simple piece of metal isn't enough to even make a scratch. Combine the piercing strength of a lance with the concussive force of gunpowder, and you might just stand a chance, even against the strongest of creatures.
At 3rd level, you do not have disadvantage when attacking targets within 5 feet of you while using a lance or gunlance.
At 3rd level, you create a gunlance, a mechanical lance with a mechanism inside which can fire an explosive shell. Gunlances have the same properties as regular lances, but weigh 20 lbs. You are proficient with gunlances.
When you take the Attack action with your gunlance, you can use your bonus action to perform a shelling attack. When you do so, all attacks you make on your turn deal an additional 1d4 force damage. Shelling attacks create a loud boom audible out to 300 feet.
Additionally, you gain proficiency with smith's tools. If your gunlance is lost or broken, you can build a new one. This process takes 1 week of work and requires 150 gp worth of supplies.
When you reach 7th level, you have learned to use lances and gunlances one-handed in conjunction with a shield, even when not mounted. When you wield a lance or gunlance one-handed while not mounted, its damage die decreases to 1d8 piercing damage.
At 10th level, when you score a critical hit using your gunlance, you can roll the weapon's damage dice one additional time and add it to the extra damage of the critical hit.
At 15th level, when you take damage from an attack or spell that you can see while you are holding a shield, you can use your reaction to halve the attack or spell's damage against you.
When you reach 18th level, you unlock the true power of your gunlance, installing a small dynamo of magical energy within its body, known as wyvern's fire. As an action on your turn, you can make a single melee attack using your gunlance. Your gunlance discharges a massive burst of energy, which deals 8d8 force damage to the target on a hit, or half as much on a miss. On a roll of 1, it deals no damage.
Once you use this feature, you must finish a short or long rest before you can use it again.
10/28/16: Wyvern's Fire now deals half damage on a miss and none on a crit miss.