Terra steel can be turned into blocks and nuggets just like any other metal, it can also be used to make tools and armour.
The Terra Steel armor is a slight upgrade from Mana Steel, providing diamond level protection, 70 Mana will be used from the player’s inventory (from a Mana Tablet or Mana holding ring) per-point of durability repairs as well as a small knockback resistance per item worn.
Wearing a full set of Terra Steel armour will grant you the following bonuses:
The Terra Steel Headpiece can also have Will’s added to it to grant extra bonuses, these Will’s only drop from the hard mode version of the Gaia Guardian (more on this here), although these are not available until much later into Botania it's good to know what is in store:
These Wills will only apply when you critically hit your target.