A class of items that, when possessed, make certain types of mobs ignore you.
Each requires you to have String and 6 "Heart Pearls"

Each item will work on one specific type of entity and require reasonably expensive intermediary components to craft. Recipe thoughts:

Zombie: Zombie Heart x 6 + Zombie Flesh x 2 + Bone = Zombie Heart Pearl

Pig Zombie: Zombie Heart x 6 + Raw Porkchop x 2 + Gold Ingot = Pig Zombie Heart Pearl

Skeleton: Rib Bone x 6 + Bone x 2 + Flint = Skeletal Heart Pearl

Wither Skeleton: Withered Rib x 6 + Bone x 2 + Wither Skull = Withered Heart Pearl

Creeper: Catalyzing Gland x 6 + Gunpowder x 2 + Bone = Creeper Heart Pearl

Ghast: Catalyzing Gland x 6 + Ghast Tear x 2 + Infernal Core = Ghast Heart Pearl

Spider: Chelicerae x 6 + String x 2 + Spider Eye = Spider Heart Pearl

Cave Spider: Chelicerae x 6 + Spider Eye x 2 + Iron Ingot = Cave Spider Heart Pearl

Magma Cube: Magma Cream x 6 + Blaze Rod x 2 + Infernal Core = Magma Cube Heart Pearl

Blaze: Blaze Rod x 6 + Magma Cream x 2 + Infernal Core = Blaze Heart Pearl

Enderman: Ender Pearl x 6 + Eye of Ender x 2 + Nebulous Heart = Ender Heart Pearl

These are done.