Question: I need a platform that lets me build and share my own stories and themes with others.

If you want a platform to create and share your own stories and themes with others, Lovelace Studio is worth a look. It offers an MMO sandbox experience where you can create, cultivate and interact with meaningful content alongside others. The platform employs AI-powered toolkits to help define and customize assets, stories and themes within generative sandbox realms. It has a community-oriented design with guilds and other activities, so it's a good fit for people who like collaborative storytelling.

Another good option is Novelcrafter, an all-purpose novel writing tool. It's a full-featured writing environment with a personal Wiki for storing story notes, multiple writing modes and AI tools to help you along the way. The tool can be used for solo writing or collaboration, so it's good for different writing styles and projects. You can try out some of its features with a 14-day free trial, and there are several pricing tiers to match your needs.

If you're more interested in AI-assisted writing, StoryNest.ai is a more powerful tool for storytellers who want to create compelling stories in a variety of formats, including short stories, novels and interactive fiction. It's got character creation tools, world-building abilities and AI-assisted editing and proofreading. It's got collaborative editing abilities and several pricing options, including a free trial, so it's good for writers who want to use AI to help them tell their story.

Last, NovelAI is a subscription-based service that uses AI for authorship and storytelling. It's got tools to create stories, to visualize characters and to create interactive fiction. With features like customizable text adventure modules and a lorebook to house world-building details, NovelAI is geared for writers who want to create something new and compelling. The service has several pricing tiers, including a free trial, so it's accessible for light or heavy use.