For Nightblood: it's as if Shashara read Elric and decided to make a more decent sword, so she made Nightblood. As for Dragnipur, I think it's a more perfected, well thought-out and clearer version of Stormbringer. And of course both are more evil than Nightblood. If Nightblood encountered them, he'd want to kill them instantly.

Dying delivers one into the river of darkness, that passes into and out of the ruined city of Kharkanas, the womb long dead, long abandoned. Into the river, and the river must travel on, ever on.

Caladan Brood sealed the barrow, and upon the capstone of bleached dolomite he set a symbol, carved deep into the stone's face. An ancient Barghast glyph, its meaning precise and yet a thing of countless layers – although this is known only to those who in life come to face it directly.

A single Barghast glyph.

Which said Grief.