Story to Get the Onyx Lord’s Greatsword – Elden Ring
Location: You can find the Onyx Lord greatsword in the sealed Tunnel within the capital city.
Travel to Altus Plateau.
Unlocking this area can be done by defeating the Magma Wyrm makar in the Ruin-Strewn Precipice.
You can use the structure in the boss's arena center for protection and to use flasks.
Its attack animations are extremely recognizable, so you need to reposition accordingly.
Once at Altus Plateau, you have to travel east towards Altus highway junction.
How to Get: Knights, Ballistas, and catapults are scattered around the area heading to the junction, so you have to move fast and do your best to avoid their attacks.
You will find two tree sentinels waiting at the end of the junction but you can simply run past them and enter the capital outskirts.
When you reach the capital, head straight into the field then travel towards the cliff.
You have to follow the rocky path until you reach a lake at the bottom.
After that, continue traveling south to the opening of the cave.
There is a hidden entrance right next to a summoning pool.
Simply hit it to reveal the sealed tunnel.
Travel to the southwestern section of the area to unlock another hidden path.
On this level, travel southeast into another room, but be wary of vulgar militiamen guarding the entrance.
There are several abnormal stone clusters hidden in the area that will explode as soon as you go near them, so move as far away as possible.
Then you will need to travel south until you reach another hidden path. Jump down but pay close attention to where you drop or risk dying instantly.
Continue towards the next room to battle the Onyx lord.
And summon your spirit Ashes as soon as the battle begins to draw the Onyx Lord's attention elsewhere.
Its attacks can easily be telegraphed so be prepared to dodge.
The AOE ability of this foe can be devastating so keep your distance.
Once the Onyx Lord falls, you will acquire its weapon.
The Onyx Lord's Greatsword has 118 physical attacks, 76 magic, and 100 critical damage.