Abyss 1.9 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The software lies within Internet & Network Tools, more precisely RSS Tools. This free software for Mac OS X was originally developed by Xavi Moll.
From the developer:
Abyss offers an easy way to store links for later reading. Every link that you store will be available to you on your iPhone, iPad, and Mac, forever. You'll never have to sign in to any external service because all your data is safely stored on your own personal iCloud account and only you have access to it. Everything that you save on your iPhone will also appear on your Mac and on your iPad without you having to do anything.
You may want to check out more software for Mac, such as Abyss Web Server, The Saint: Abyss of Despair or Abyss: the Wraiths of Eden, which might be related to Abyss.