He starts talking rapidly, with animated facial expressions. “Oh, you’ll love it. It’s as hard as any alloy, but it’s found in the roots of trees that have sucked up the right metals from the ground. There’s no magic to it, but it can repair itself, just like it was a real plant, and if someone hits it in just the wrong way, it can even corrode their weapon.”
[Rules text:
An item made from living steel repairs damage to itself at a rate of 2 hit points per day, or 1 hit point per day if it has the broken condition. Items not primarily of metal are not meaningfully affected by being partially made of living steel.
Armor and shields made from living steel can damage metal weapons that strike them. Whenever the wielder of a metal weapon rolls a natural 1 on an attack roll against a creature wearing living steel armor or wielding a living steel shield, the item must make a DC 20 Fortitude save or gain the broken condition. If the weapon already has the broken condition, it is instead destroyed. Living steel cannot damage adamantine weapons in this way.
]