When you are about receive damage you may conjure a magically strengthened ruby shield to block or reduce that damage. The ruby shield has 20 hit points and is resistant to fire, cold, lightning, necrotic and poison damage. It is vulnerable to radiant, thunder and force damage. 

If the shield is reduced to 0 hit points it breaks and any remaining damage is carried over to you. If the amount of damage carried over is equal to or greater than the hit points the shield had when you cast the spell, you receive an additional 50% of that damage. 

Once you have cast this spell you cannot cast any spells greater than a cantrip until the end of your next turn.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the ruby shield is created with 20 more hit points for each slot level above 1st.