Crystal Erchius Fuel
An unstable crystalline substance, mined from moons and used as FTL fuel.
It can be mined like any other ore, and will fuel ships for twice the inputted material. Mining it will cause the Erchius Ghost to pursue the player relentlessly. If the player has the Spooked debuff from being on any Moon, having Erchius Fuel in their inventory will cause them to glow purple; the more fuel the player is currently holding the brighter they will glow.