I just got done with the challenge earlier this morning, something that could contradict about what you said. Edit 1/ Edit 3 - My reward status: Calcified Fragment / Worm Gods' Servant Emblem / 310 and 320 Numinous Web (Warlock Artifact) / 320 Harrowed Quillim's Terminus (Raid LMG) / 310 Defiance of Yasmin (Raid Sniper). Edit 2 - Don't know if you need different aura holders each time, (probably so). Don't know if deaths or rounds matter, i finished it in 2 rounds w/ 2 guardians down by the 2nd round. More knights do not spawn (at least at top). Edit 4 - You can lose the aura (die w/ the aura). I think the 320 random drop is true, but i also think that each weekly challenge comes with a weekly 320 weapon or armor reward.