@tt-bot-dev/extension-runner is the heart of tt.bot's extensions powered using isolate-vm.
Extensions (obviously) extend the base tt.bot with community-made features. While the current extension system provides tools to make non-standard commands, it can be easily wrapped for other activities. For security reasons, the untrusted user code runs in a separate thread using a separate JavaScript environment (using isolated-vm) and the public API wraps the underlying Eris objects in the main JavaScript thread.