Perhaps you will be interested
This item is a very rare drop from Mistress Sassz'ine in the Tomb of Sargeras on all difficulty modes, including Raid Finder.
Here you can buy Abyss Worm for EU or US Servers.
You'll get guide for getting Abyss Worm
You'll be able to get Abyss Worm mount
After patch 10.2 might will need character transfer for access to BMAH