Load into expert court of blades throw on eyes of tomorrow, once you kill everything rinse repeat. Keep in mind 2 banes usually spawn, may take a bit of time but by far the fastest way without much trouble fighting others for the kill, That's how I did it 🍻 Not sure exactly how many runs. but as a player who has completed every single weekly challenge since it's inception into the game, I try to find the fastest and most efficient way, and this is it.

just load into any expert nightfall solo