Campfire
It was only after around 10 minutes of laying there that Lumen had regained the courage and strength to essentially drag himself back to the shore.
He was so tired that he only had time to light a simple fire before he collapsed on the spot next to it, entering a deep slumber.
3 hours later, he finally awoke, still exhausted and somewhat weak from his experience of nearly falling entirely into the abyssal lake. The experience had left him both mentally and physically out of it, as he simply sat there staring at the light from the dimming campfire reflecting off of the water, contemplating his situation and how he could even get through this luck based trial.
'Surely there is some hidden component to this, there is no way the system expects anyone to ever have the chance to see what lies at the end of all of these trials if it puts in place such unfair and completely unrealistic challenges that would probably never be overcome in billions of years....'