Reinforced Exoskeleton Plates are useful to create armor in this mod. They're crafted by nine exoskeleton plates.
Using the regular crafting recipes, reinforced exoskeleton plates can be crafted into armor as tough as diamond and more durable. It's much less enchantable though. It can then be made into special gear
Additionally, putting four in a square into the crafting table will create reinforced exoskeleton blocks, which are really tough and immune to explosion damage.