In order to access this primal you must have first completed "It Kills with Fire (city)" and have "Ifrit bleeds we can kill it" active.

In order to access the chest for the win you must have an Inferno Lamp, this can be obtained in one of 2 ways, 1) Get the Lamp directly from the NM leader of Zahar'ak or 2) Collect 5 Inferno Tapers from the standard mobs in the area and have them made into a Lamp by Louisoix

Combat Strategy

After tank gets initial hate built, usually 15~30 seconds build, everyone should move into their positions.
Mages to the left or right at the outermost range of your casting. Melees to the sides and back at all times, do NOT run in front.

When Ifrit jumps, melees should stack on top of the tank.

When cracks occur run off of them, AWAY from the tank, never toward. Cracks only appear below those not in 1st on the hate list, so unless things go horribly wrong the tank should never be at risk.
*Edit (Apologies) Also don't want to run towards the healers.

When spikes pop everyone not the tank and healers need to destroy them as fast as possible, each one that is destroyed will weaken the up coming hellfire with all four destroyed everyone should be able to survive.

Most of that is rinse and repeat right up to the end. The AoE of cracks and the speed/frequency of jumps will increase and he will eventually multiply, stay clammy and you'll get through it.