Dyrnwyn

Unsheathed, it sizzles and spits with deathless fire, an impossible blade.
Overview
Dyrnwyn is a one-handed sword added in the 
Each fragment is found at one of the three Mysterious Locations. The fragments weigh 0.5 each, do not stack, and are not renewable, so under normal settings only one Dyrnwyn can be crafted per world. If item drop rate is increased in the world settings, additional fragments can drop and more copies of the sword can be made.
Dyrnwyn has four quality levels. Its base stats and upgrades are:
- Quality 1: 145 slash, 10 fire, 200 durability
- Quality 2: 151 slash, 10 fire, 250 durability
- Quality 3: 157 slash, 10 fire, 300 durability
- Quality 4: 163 slash, 10 fire, 350 durability
Its crafting and upgrade costs are:
- Crafting: 1 Dyrnwyn hilt fragment, 1 Dyrnwyn blade fragment, 1 Dyrnwyn tip fragment, 20
Flametal, 1
Bloodstone
- Upgrade to quality 2: 10 Flametal, 1 Bloodstone
- Upgrade to quality 3: 20 Flametal, 2 Bloodstone
- Upgrade to quality 4: 30 Flametal, 3 Bloodstone
- Full creation and upgrades to quality 4 require a total of 1 fragment set, 80 Flametal, and 7 Bloodstone
Because Dyrnwyn is a slash-and-fire weapon, it benefits from being used against enemies that are vulnerable to either damage type. For Ashlands combat, weapons that deal spirit damage such as 

The sword also has a real-world mythological inspiration. In Welsh tradition, Dyrnwyn was a legendary sword associated with Rhydderch Hael and was said to burst into flames when wielded by a worthy man. Earlier in development, the weapon existed before the Ashlands update as an unobtainable console-command item with different stats and a different internal ID, but its current craftable form is the official version tied to Ashlands progression.
Official description
Unsheathed, it sizzles and spits with deathless fire, an impossible blade.