on the map, you see the Mystic Circle on the far west of the maps on the british isles.
If youre even lowly geared, you can fit yourself against the Wolf Heart who you need to kill in order to get the Weapon and Scale Mail.

He is quite the fast and takes a lot of damage, but keep pressing W to advance into battle before he has time to react and hit him. kill him fast, he has a backup of 5 or so robbers coming behind you in 10 secs after talking ends.

after killing him, you obtain the weapon. stock stats are few points better than the best regular sword (rich sword).

Head to Aileach town to the north on the same isle. Go stroll around the Town, go down the hill from the fort into the city, and find the weaponsmith.

Talk to him while taking out your sword into your hands, and he asks if he can refine it. (Cost for me was 22k.) allow him to do it for you, and voila.

Stats are as follow

Name: Balanced Draguandil (im not sure if you can make it even better)
Speed: 93
Reach: 95
Damage Cut: 38
Damage Piercing: 21
base price increase 9751

Spread it so everyone can get the sword :)

You can also double-temper it for 30k Pennings, and make it Tempered Draguandil. thats the longest you can temper a single piece of weapon, i havent found yet a sword that can be tempered to higher amount than this one. Only if its able to be achieved, to get Lord/Kings sword drop (Godelic Noble Sword) somehow, then that would be better.

Stats are as follow

Speed 95
Reach 95
Damage Cut 39
Damage Piercing 23
Base Price increase 15000