Enderium is an advanced alloy added by Thermal Foundation. It consists of Tin, Silver and Shiny Metal in a 2:1:1 ratio, with Resonant Ender added to the mix. The alloy is very strong, and requires Pyrotheum Dust to smelt into ingot form.
Empty Buckets are returned upon crafting Enderium Blends.
Due to how strong the alloy is, Enderium is most commonly used to create the highest tiers of machines and devices in Thermal Expansion and Thermal Dynamics. Other than that, it doesn't serve much purpose on its own.