A wall to your back is just as good as another sword-arm and you excel where others find their restricted fighting techniques undone by a low ceiling or narrow hallway—castled lords and fort commanders pay handsomely for your blade.
Beginning when you choose this archetype at 3rd level, while adjacent to an ally or wall you gain a +2 bonus to AC as well as advantage on checks made to avoid being disarmed, fall prone, or resist a shove.
Starting at 7th level, you master a broad stride and adroit footwork that grants you an undeniable tactical mobility. Any ally granting you a bonus to AC from the flanked defense feature gains a +1 bonus to AC and increases your AC bonus to +3. If you have the Protection fighting style, you may use it to benefit allies within 10 feet instead of 5 feet.
Protection Fighting Style
At 10th level, you learn the Protection fighting style in addition to any others you know. If you already knew that fighting style, when you use the feature both the attack you use it against and the next attack made against your ally before the end of the round are at disadvantage so long as your ally remains within 10 feet.
Back to the Wall
Beginning at 15th level, while within 5 feet of a wall you gain advantage on your first attack roll each round. When you are in a corner or a tunnel with a wall within 5 feet of two sides of you, you gain advantage on all attack rolls.
Starting at 18th level, any time that you are benefiting from your flanked defense feature you also benefit from back to the wall, treating your allies as if they were walls (gaining advantage on all attack rolls if adjacent to two allies).
Dungeon Archetypes. Copyright 2016 Mike Myler, published under license by Legendary Games; Authors Mike Myler.