Tetsu armour is a set of degradable melee armour unlocked via Player-owned ports. 85 Defence and Constitution are required to wear it. It can be made at 90 Smithing in the port's workshop which is not boostable. Plate is the trade good required for its production.
Before the armour can be made, the ability to make the pieces must be unlocked. This is done by collecting 4 forgotten scrolls per armour piece. A total of 12 scroll pieces are required to be able to craft all 3 pieces of the armour.
The armour comes in two versions, tradeable and untradeable ('Superior'). The Superior version has higher stats than the tradeable one and lasts 12 hours of combat, compared to the regular version's 10 hours. The Superior version can be repaired, but the tradeable version cannot and will degrade to nothing. The repair cost of the Superior armour set is &00000000021000000000002,100,000 at level 99 Smithing.
Upon death: Tetsu armour will degrade slightly if a player dies (while it is equipped), and doesn't choose it as a saved item. If the armor is in the inventory, no charge is lost. An easy way to avoid degrading is to unequip the armor before death.