Swarmskin

You conjure thousands of tiny creatures, such as spiders, rats, scorpions, centipedes, or a similar type of beast.  The swarm covers your skin and outerwear as the creatures crawl around you harmlessly, and also spreads to nearby surfaces within your space.

You gain 4d4 + 4 temporary hit points which last for the spell's duration.  Once the temporary hit points are depleted, the spell ends.

While you have these hit points, you can use your action when you are hit by a melee weapon attack to gain resistance against bludgeoning, piercing, and slashing damage from that attack.  Additionally, the creature that hits you takes piercing damage equal to 2d4 + your spellcasting ability modifier.

Further, you have advantage on ability checks to initiate, avoid, or escape a grapple.  A creature in a grapple with you suffers piercing damage equal to your spellcasting ability modifier immediately when the grapple is initiated, and again at the end of each of their turns.

At Higher Levels.  When you cast this spell using a spell slot of 4th level or higher, the temporary hit points increase by 1d4 + 1 for every slot level above 3rd, and the damage dealt by the spell's reaction effect increases by 1d4 for every slot level above 3rd.