The Blade of Death - Elden Ring
Black knife Assassin dropped the black knife who is guarding the sainted Hero's grave dungeon in Atlus plateau.
You either get two halves of the dectus medallion to operate the Grand lift of Dectus, to gain access to Atlus Plateau.
Or defeat the Magma Wyrm on top of the Ruin-Strew Precipice to gain access to a lift that leads you to the place.
The grave of the Sainted Hero can be found west of the capital city.
Black knife Assassin
The dungeon's entrance will be guarded by a black knife assassin. Defeat it to acquire the black knife.
This one is nimble but has low poise, like all black knife Assassins.
Be careful of the ranged attack from the black knife.
The poise of this weapon is so low that some of its attacks can be interrupted by another attack.
The black knife is a weapon that requires 8 strength, 12 dexterity, and 18 faith.
Its special attack "Blade of Death" is a slow process. First, it takes time to wind up the attack. Then, once it's charged, it fires a holy projectile that deals holy damage over time.
When dual-wielded alongside another knife to maximize its attack speed the black knife is great.
Overall, this is a useful weapon for players that are going for a faith and dexterity build.