Fighter: Arena Master

No matter where you originally started in life you have found yourself at your lowest of lows; forced to risk life and limb in the Arenas. However, unlike most, you have learned to embrace this new lifestyle and survive the onslaughts of the Arena. 
Most Arena Masters were likely thrown into the Arena as a form of punishment, however, there is redemption for the few that manage to survive. Arena Masters find themselves becoming local celebrities as long as they keep winning. Whether it is a horde of Axebeaks or a Gang of Bandits you will find a way to overcome the challenge despite being outnumbered. 
Despite earning their freedom long ago, Arena Masters consider the Arena their job. With the pay varying from warrior to warrior and from Arena to Arena some Arena Masters live amongst the elite while others barely make by. 

I'll Take You All On

One against three? I'd call that a fair fight!
Starting at 3rd level when you choose this archetype you are unable to be surprised or flanked. 

Knowledge of Beasts 

It's a slow day in the arena if I only have to fight one Owlbear!
Starting at 3rd level when you choose this archetype you gain proficiency in either Nature or Animal Handling. If you already have proficiency in both of these skills you may choose a new skill to gain proficiency in. 

Strength Without Numbers

I often find that I am at my best when I am outnumbered! 
Starting at 7th level if you were to be considered flanked by normal standards your AC increases by +1. This increases to +2 at 15th level. 

Additional Fighting Style

To survive in the arena you must learn to adapt. 
At 10th level, you can choose a second option from the Fighting Style class feature.

Taste of Their Own Medicine 

I guess you could say I have learned a thing or two from the beasts. 
Starting at 15th level you gain the ability to cast the spell Conjure Animals. You cast this spell at 5th level and may use a Bonus Action to cast the spell. You can only cast this spell once. You regain the spell slot upon completing a Long Rest. 

Survivor

Despite everything I have survived. 
At 18th level, you attain the pinnacle of resilience in battle. At the start of each of your turns, you regain hit points equal to 5 + your Constitution modifier if you have no more than half of your hit points left. You don't gain this benefit if you have 0 hit points.