Pity may have kept Bilbo from killing Gollum, but not everyone shares that compassion. Gollum died after leading the hobbits into Shelob's lair but before he bit the Ring off Frodo's hand.
What happens when Frodo decides to keep the Ring?
1. One-Shot Story (option one): Sam won't accept Frodo's decision. They've gone too far to fail now. Will he fight Frodo to destroy the ring himself? If he gets the Ring, will he be able to succeed where his friend failed?
2. One-Shot Story (option two): How does Gollum die? Who kills him and why? Was it Frodo? Did he finally go mad and kill the wretch so he'd stop trying to take the Ring? Did Sam, who knew the truth about Gollum's desire for the Ring, feel it was the only way to protect Frodo? Perhaps Sauron's servant (who sent him on an errand of mischief) discovered he failed and punished him for it?
Maybe Gollum wandered to the west side of the mountains in search of food and water or on another errand. Did Faramir find him wandering alone and assume he'd killed the two hobbits? Was it Legolas, who was angered by the shame Gollum brought to the woodland elves by escaping their dungeons? Or was he killed by someone completely unexpected?
3. Short Story: As Isildur's fate was drastically effected for the worse, so is Frodo's. What happens to the Hobbit? Describe everything from the moment he keeps the Ring until it arrives in Sauron's possession.
4. Novel-length Story: Frodo finds himself taken captive by Sauron's armies. Now the Dark Lord has his Precious back. What havoc does the hobbit's failure cause for Middle Earth's people? How does the land change in nature and civilization? How does the Ring get recaptured and destroyed?
For "extra credit", don't add Original Characters.
5. Other Inspiration: Tell another story inspired by and related to the basis of this challenge.