Copper monstrosities' acid

You learn to call on the ancient acid to serve your commands. You gain the following benefits:

• When you roll acid damage for a spell you cast, you can reroll any roll of 1 on the acid damage dice, but you must use the new roll, even if it is another 1.
• Whenever you cast a spell that deals acid damage, you can cause acid to bubble below you until the end of your next turn. The acid doesn’t harm you or your possessions. While the acid is present, when a creature hits you with a melee attack, you can use the acid to shield you and take away 1d4 damage also when any creature within 5 feet of you that hits you with a melee attack takes 1d4 acid damage. When you get to higher levels you can increase the 1d4, at lv 8 is 1d6, lv 12 is 1d8