Hydra is attacking porcupine? Well, actually not. Because Hydra is Lerna.js and porcupine is a SharePoint Framework solution with library components. Most likely you've heard about SharePoint Framework and library component, but not about Lerna. Lerna is

A tool for managing JavaScript projects with multiple packages.

Sounds simple, but probably still not very clear. First of all, it works only with JavaScript (and of course, TypeScript, for simplicity I use JavaScript term) projects. Some companies have JavaScript projects with lots if modules developed internally or publicly (it doesn't matter) in separate git repositories. These modules usually reference each other in the corresponding package.json files. Making changes across different modules is an extremely difficult and messy task. To solve these and other issues, some companies organize their projects in multi-packaged repositories (i.e. one git repository with many JavaScript packages):

Lerna is a tool that optimizes the workflow around managing multi-package repositories with git and npm.

Now it becomes a little bit clear what is Lerna. However, how does it correlate with SharePoint Framework and library components?

Imagine you have a solution with SharePoint Framework web parts and you want to add a new library component to share code across web parts. A new library component always creates a new JavaScript package (package.json). In the end, you will have two JavaScript packages in your repository - one for SharePoint Framework web parts and another one for the library component. So you have a multi-package repository and it's a good place to add Lerna to reduce the mess!

Actually, you're not limited in using Lerna with library components only. If you have a few separate SharePoint Framework solutions in one git repository, you can add Lerna to simplify package management. More...