Overtime

After being weary of every possible danger for so long, you develop the ability to enter a period of hyperfocus for a short period of time, but at a cost. Upon being attacked, you can use your reaction to trigger this feat (Provided that this feat isn't already active, of course.) When triggering this feat, you gain the following benefits until the beginning of the turn of the creature you used your reaction against:

• When a melee attack of any kind is made against you, you can choose either: 
  1. Make a melee attack back, negating damage equal to the damage you would deal. Add your proficiency bonus to the melee attack roll.
  2. Use a spell to strike back, imposing disadvantage on their attack roll if your attack lands. Your spell deals half-damage.
• When a ranged spell targets you, directly or indirectly, you can choose to either:
  1. Make a ranged attack of any kind (Spell included) in an attempt to force a concentration check.
  2. Take preventative measures (Add your proficiency to your AC for ranged spell attacks and add proficiency to saving throws.)

However:

• You gain 1 point of exhaustion if you use this feat more than once every 3 rounds
• You must make a DC 15 WIS save or gain a temporary -1 to AC, all saving throws/ability checks, and attack rolls (Debuff duration 1 round) when this feat ends. 

You can use this feat a number of times equal to 1 less than your Wisdom modifier per long rest. You also regain 1 use every short rest.

(Note: This is a BETA feat. It's probably not balanced.)