Adrenaline. Whenever the acro takes damage while in its shield stance, it gains a number of adrenaline points equal to the damage taken. Once it accumulates 30 or more points, it immediately enters adrenaline mode for 1d4+1 rounds. In this state, the acro gains resistance to bludgeoning, piercing, and slashing damage, is immune to the frightened and stunned conditions and the effects of exhaustion, and can make two additional attack when it takes the attack action.   Keen Hearing. The acro has advantage on Wisdom (Perception) checks that rely on hearing.   Shield Stance. As a bonus action, the acro can switch between it's shield stance and normal stance. In shield stance, the acro's walking speed is reduced by half and it cannot take the dash or dodge actions. If the acro does not take damage for a full round, it is forced to return to its normal stance at the end of its turn. The acro breaks its shield stance if it is incapacitated or knocked prone.