Oh, I was able to figure out that the 2nd NPC in level 4 was standing on an invisible platform so that's not an issue for me! Where I got stuck was the uppermost long horizontal corridor after jumping across the chasm and reaching the riddle. One of the eyes started watching me as soon as I reached that corridor, and since I couldn't solve the riddle (is that what you mean by getting the relic?), I didn't have the extra brightness and couldn't run down the corridor in time.
Viewing post in World Alert: Purge the Dark jam comments
Yeah that's the issue with level 4: if you jump down to get to the riddle (relic) but don't solve it, you can't make it past the eye corridors - and there's no way back up to the platformer solution without restarting the level - something I missed during development. Try using that same NPC hint elsewhere.