Parasitic Devotion

The parasite living inside you has become utterly devoted to the host's protection. When a critical hit is rolled against the player the parasite will either:

a) form a protective shell against a magic spell, reducing the damage by 1d6 from level 3, increasing by 1d6 every 5 levels.

b) as a reaction, when a melee attack is a critical hit the parasite lashes out. It deals 1d6 piercing damage starting at level 3 and increasing by 1d6 every 5 levels.