Armor of Shifting Defence

The protection this armor provides is fickle. Roll a d20 every time you are targeted by an attack that requires an attack roll. The AC against that attack is 1d20 + your dexterity modifier, or 10 + your Dexterity modifier + your Constitution modifier, whichever is higher. 

On a roll of 20, you gain resistance to bludgeoning, piercing and slashing damage until the start of your next turn.

On a roll of 1, you instead gain vulnerability to bludgeoning, piercing and slashing damage until the start of your next turn. 

The breastplate and shoulder protectors of this armor are made of leather that has been stiffened by being boiled in oil. The rest of the armor is made of softer and more flexible materials.

Notes: character proficient in light armor, Buff, Debuff