The ouroboros pouch acts similarly to the Druid pouch, but has an infinite number of uses. After raising Jayene Kliyn's level to 99 in the Temple Trekking minigame, it can be obtained by clicking "druidic" in Jayene's menu on the noticeboard in Burgh de Rott.
The pouch uses itself when a ghast is in your area which means you don't have to click.
The pouch can be added to the Slayer section of the tool belt.
In the real world, the Ouroboros is a symbol that is represented by a snake or serpent eating its own tail which in turn represents cyclicality, or constant re-creation as soon as things end. It is a representation of infinity, relating to the infinite uses of the pouch.