How do you get the black blade in Dark Souls 3?

Darkmoon Blade Dark Souls 3 Wiki

Dark Sword Moveset (Dark Souls 3)

I did it… I finally got the Darkmoon Blade. My build is complete. : r/darksouls3

This might be obvious but doesn't the onyx blade look like the hollows tried to recreate the firelink greatsword? : r/darksouls3

I know this may be a stupid question, but what would you guys say is the closest real life equivalent to the dark sword from Dark Souls? : r/SWORDS

Dark Souls III Onyx Blade by MichelePaludetti on DeviantArt

Dark Blade Dark Souls 3 Wiki

Covenant: Blade of the Darkmoon achievement in DS3

Frayed Blade Dark Souls 3 STL Digital Model 3D Print Cosplay

DARK SOULS III How To Find Vow of Silence, Dark Blade, & Dead Again