There was always fighting for sport in the alleys. No-holds-barred fighting. Ruthless competition in which the loser usually pays with his life; or an arm or leg, if they're lucky..

To survive in these arenas the only rule a Brawler needs is to clear your mind of all rules. 

 

Brawlers are ruthless, relentless, and unconventional fighters, usually found in fighting pits and underground arenas. Though never formally trained in martial combat, a brawler is taught to fight by a simple teacher "Survival of the fittest".   Brawlers are usually keen and observant, they constantly seek to learn and adopt new fighting techniques into their repertoire. In the heat of combat, a Brawler fights only for survival and to that end, there is nothing they won't do. Throwing sand in an opponent's eyes,  Throwing poisoned caltrops at their feet, breaking a bottle over their head, and stabbing them with the shards;  to a Brawler, anything can and will be a weapon if the situation calls for it. 

Improvised Fighting

 Starting at level 3, when you choose this archetype, you become proficient with improvised weapons. You can use either strength or dexterity for attack and damage rolls made with Improvised weapons. When wielded by you improvised weapons have a 1d8 damage die and can deal slashing, piercing, or bludgeoning damage depending on the nature of the attack. Additionally, the first time you attack a creature with a unique improvised weapon you have advantage on the attack. You can't gain advantage with the same improvised weapon more than once for the duration of combat. 

Brawler Instincts

Starting at 3rd level, You have developed a knack for noticing the moment that a fight is about to break out and honed your reflexes to react accordingly. You gain a +5 bonus to your initiative rolls. Additionally, when you take the attack action against a creature that hasn't acted yet in the initiative order you can make one additional attack as a part of the same action. 

Cheap Shot

Starting at level 7, you have learned to exploit any advantage you can take to debilitate your opponent. When you have advantage on an attack roll, you can choose to forgo the advantage to make the attack a cheap shot as you aim to strike below the belt or in other unconventional areas. If the attack lands, the target must make a Constitution saving throw against a DC equal to 8 + Your proficiency + Your Strenght or Dexterity Modifier. On a failure, the target is stunned until the end of your next turn. Once you successfully use this feature against a target you can't do so again for the duration of combat. 

Grit your Teeth

Starting at level 10, Your grit and determination in battle allow you to shrug off blows and keep on fighting. When you have less than half of your maximum hit points left, you can use a bonus action to spend one of your hit dice to gain a number of temporary hit points equal to a roll of the hit dice + your constitution modifier + your fighter level. Once you use this feature you can't use it again until you finish a short or long rest. 

Opportunistic Brutality

Starting at level 15 You have learned to maximally exploit your opponent's moments of weakness. Any attack that you land against a creature that is either surprised by you or is stunned or restrained is considered a critical hit. 

No-holds-barred

Starting at level 18, Your drive for victory knows no bounds and there is nothing you won't do to win. In combat, during each creature's turn except your own you can take a special reaction to make an Opportunity attack or Use an item.