Zurvan was added in patch 3.5 of the Heavensward expansion.
Zurvan becomes available at level 60 as part of the “The Last Pillar to Fall” quest, which is given by Unukalhai – Mor Dhona – The Rising Stones (X:6, Y:5).
The trial has a minimum ilevel of 235 to enter and rewards you with:
Allagan Tomestone of Poetics: 15