There’s a couple of things wrong here
- Shelob wasn’t killed by Sam (as stated by another user). She was wounded greatly, but definitely not mortally, and she retreated back into her caves to heal
- Ungoliant (the mother of all spiders, including Shelob) did not eat “the original sun and moon”. She drank the light of the two trees which provided light to Arda before the sun and moon, causing them to rot and die.
- The two trees weren’t the original sun and moon. Before the two trees, there were the two lamps which stood on or near the poles of Arda and were the original lights of the world. I don’t think it’s fair to call either the lamps or the trees iterations of the sun and moon since the idea of a day-night cycle didn’t exist prior to the sun and moon, at least in how we think of it. During the age of the two lamps (the Spring of Arda), both lamps shone constantly (no transition for time of day). During the age of the two trees, the trees would bloom throughout the day on a cycle, alternating which one was in full bloom. This is closer to day and night, but the trees shone so brightly that dark night never existed. Plus, the trees blooms mingled twice a day, essentially creating two “noons” per day
That’s a very good point. Sam’s achievement shouldn’t be understated, as he is the first and last mention of any harm coming to Shelob. Beren did pass through Shelob’s birthplace in the first age as he traveled through Ered Gorgoroth (he was the only one of the children of Ilúvatar to do so), and I wonder if he crossed paths with her, as she was the final and mightiest of Ungoliant’s spawn and therefore must have had a place of dominance amongst the other great spiders there.
Imagine being a creature born of an ever yawning abyss, living for eons; and possibly the second mortal to evade your maw is not Beren, greatest of men, but rather Samwise, the humblest of the children of Ilúvatar, and not only did he evade her grasp, he wounded her and stole her finest meal in what was probably hundreds of years. Sam was truly one of the most valiant souls to ever walk Arda