The Sightless Eye is a new Legion 7.0 currency that is earned and spent in the Dalaran sewers. It can be used for a variety of merchandise, like all kinds of professional recipes and pets. These recipes can be learned just need 1 professional skill.
How to acquire the Sightless Eye?
1. Opening all random refresh chests and fishing on the Sewers, three chests here: Big, Medium, and Small Chest. It can be fished in the waters around the Black Market Auction House. Additionally, the item Fel Chum can be purchased from Oxana Demonslay. There is a chance to obtain Sightless Eyes by using it.
2. Killing the Dalaran elite monster will obtain the Sightless Eye, and the refresh is random and very frequent.
3. You can bribe Sewers Guard Captain with 50*Sightless Eye to ask all guards back and make the area free. Then all players can attack each other(including friend players ) to get the Sightless Eye.
Once you loot 20,000 Sightless Eyes, you will obtain the achievement Underbelly Tycoon, which rewards the Ratstallion mount. 
In the nearly future, there is no order, and it will be very dangerous.