The Ferrous Wroughtnaut is a large Knight, which can be found underground in Minecraft. Specifically, it can be found inside the Wrought Chamber, which is a large room only a few blocks wide.
When you first discover the Ferrous Wroughtnaut, it will be inactive. As you get close, it will come to life, and start attacking. As you strike back, you might notice that you deal no damage at all.

The Ferrous Wroughtnaut is a creature provided by Mowzie’s Mobs. It’s a very popular mod, so expect to find it inside of many of Minecrafts modpacks.
How to Damage the Ferrous Wroughtnaut
As the Ferrous Wroughtnaut wakes up, it will begin to attack the player instantly. It’s able to conduct multiple attacks, where it might spin around in a circle, or attack from above.
As you try to attack back, you’ll hear your Sword hit metal, but you’ll deal no damage That’s because there’s only one way to damage a Ferrous Wroughtnaut.

During a special attack, the Knight will swing from above, which you need to dodge. Doing so will cause its Axe to get stuck in the ground. Only in this moment is the Ferrous Wroughtnaut vulnerable, and will only take damage if you hit it from behind.
This isn’t too obvious, but there is a hint. Take a look at the Ferrous Wroughtnaut from behind, and you’ll see a Sword lodged in its back. Each time the Ferrous Wroughtnaut has its Axe stuck in the ground, you should repeatedly attack it, until it’s defeated.
Ferrous Wroughtnaut Drops
The first item that can be dropped by the Ferrous Wroughtnaut is the Wrought Helm. When equipped, it provides the wearer with 2 Armor and 1 Knockback Resistance, and is also immune to breaking. Enchantments can also be applied to the Wrought Helm to empower it further.

Ferrous Wroughtnaut’s can also drop the Axe of a Thousand Metals. Like the Helmet, it will never break. It has an Attack Damage value of 9, and an Attack Speed value of 0.9, making it a very powerful weapon.
There are 2 attack styles which can be used with the Axe of a Thousand Metals. Right-clicking will attack in a large arc. Whereas holding down SHIFT and right clicking will slam the ground instead, creating a shockwave.