How to get the Inseparable Sword in Elden Ring

gamepur.com:

Early in Elden Ring, you’ll encounter two important characters: D, Hunter of the Dead, as well as Fia, the Deathbed Companion. These characters’ questlines are intertwined, and if you bring both of them to their conclusion, you’ll acquire the Inseparable Sword.

To kick off D’s quest, you’ll first need to acquire a Deathroot, and then speak with him in Roundtable Hold. He’ll advise you to hand the Deathroot to Gurranq. After that, advance through the main game until you arrive at Atlus Plateau. Then, head back to Roundtable Hold, and advance Fia’s questline until she kills D using the Weathered Dagger. After she kills D, you can loot his body to obtain D’s Twinned armor, a key item for getting the Inseparable Sword.

Your next stop should be the Siofra Aqueduct, located inside the Eternal City of Nokron. Right outside the twin Valiant Gargoyles fight, you’ll find a sitting man who is D’s younger brother. Talk with him, and you’ll be asked if you would like to hand over the Twinned Armor. Hit “yes” to give D’s armor to his brother.

Now, you’ll have to progress all way through Fia’s questline. This includes defeating the aforementioned gargoyles, finding her in the Deeproot Depths, fighting her champions, delivering the Cursemark of Death to her, as well as defeating Lichdragon Fortissax.

Related: Where to find Fia after D’s death in Elden Ring

After you’ve finished Fia’s questline, return to her and you’ll find that D’s brother has killed Fia. If you leave and re-enter the area again, D’s brother will be gone, but D’s Twinned armor, as well as the Inseparable Sword, will be yours to claim.