Thornskin

The visage of a thorny, crimson carapace surrounds your form, granting you protection from attacks. 

For the duration, any creature has Disadvantage on melee weapon attack rolls against you.

In addition, whenever a creature within 5 feet of you hits you with a melee attack roll, a thorn erupts from the carapace and absorbs their life essence, dealing 2d8 necrotic damage and you regain Hit Points equal to half the amount of Necrotic damage dealt.

Blootletting. When you cast this spell you can choose to expend a number of hit dice equal to the spell level at which it is cast. If one or more hit die are expended this way, the spell is altered in the following ways: 

- For the duration, any creature has Disadvantage on attack rolls against you.

- Whenever a creature hits you with a weapon attack, a thorn erupts from the carapace and absorbs their life essence, dealing 2d8 necrotic damage and you regain Hit Points equal to half the amount of Necrotic damage dealt.