Location of Legendary Armament in Elden Ring
The Ruins Greatsword is a Strength and Intelligence based sword, it is legendary quality and can be acquired from a secret encounter at the Redmane Castle Plaza. This location is near where the Starscourge Radahn fight is initiated. To trigger this fight, you’ll need to first defeat Rennala, Queen of the Full Moon, then travel to the Redmane Castle Plaza in Caelid.
Stat Requirements of Ruins Greatsword:
Str/Strength: 50
Int/Intelligence: 16
Unique Skill: Wave of Destruction
Raise the sword up high, then strike it against the ground to fire off a wave of gravitational force.
Have a great day, and as always, thanks for watching!
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I honestly thought this fight was just before radahn because I had to go through it before I fought him
UPDATE #2: It seems that I have no idea what triggers this boss fight. Some people find it waiting for them before they defeat Rennala or Radahn so if it isn’t there when you first go to Redmane just occasionally check back and it should show up eventually.
I was able to kill misbegotten warrior/crucible knight with out doing anything else in the game