Fighter Subclass: Bog Reaver

Level 3 — Bog Fury Swamp Strider   You ignore difficult terrain caused by mud, marsh, shallow water, or similar natural terrain. While in such terrain, you have advantage on Strength (Athletics) checks.   Apex Grappler   You count as one size larger when determining what creatures you can grapple.   While grappling a creature, your speed is not halved if the creature is your size or smaller.   Predator’s Mark   Once per turn when you hit a Large or larger creature with a weapon attack, you can mark it until the start of your next turn.   The next time you hit the marked creature before the mark ends, it takes an extra 1d6 damage of the weapon’s type.   You can mark only one creature at a time.   Level 7 — Reaver’s Grip Crushing Hold   At the start of your turn, a creature grappled by you takes damage equal to your Strength modifier.   Predator Dice   Once per turn when you hit a Large or larger creature with a weapon attack, you deal an extra 1d6 damage.   This increases to:   2d6 at level 15   3d6 at level 18   You cannot apply both Predator Dice and Predator’s Mark to the same attack.   Level 10 — Mire-Hardened   You gain:   • Resistance to poison damage • Advantage on saving throws against the poisoned condition • When you succeed on a Strength or Constitution saving throw, you may move up to 10 feet without provoking opportunity attacks   While in difficult terrain caused by natural environments, you also have advantage on checks to resist being shoved or knocked prone.   Level 15 — Apex Reaper   When you reduce a Large or larger creature to 0 HP:   • You gain temporary HP equal to your Fighter level • You may make one weapon attack as a bonus action   Additionally, when you hit a grappled creature with a weapon attack, you may knock it prone (no action required). Once per turn.   Predator Dice increases to 2d6 at this level.   Level 18 — Tyrant of the Mire   You project a 10-foot aura of predatory dominance.   Large or smaller creatures of your choice in the aura have disadvantage on checks to escape your grapple.   Additionally:   Once per long rest, when you hit a Large or larger creature, it must succeed on a Wisdom save (DC = 8 + PB + STR mod) or be frightened of you until the end of your next turn.   Predator Dice increases to 3d6.