PF: Fog cloud/Deeper Darkness Concealment Question

[joca4christ]

Currently running the Shackled City Adventure Path using a hybrid of PF and 3.x rules. My party is about to encounter the dark stalker in the ruins of Jzadirune.

According to PF bestiary, a dark stalker can cast bot fog cloud and deeper darkness at will. Both grant concealment. My question is, does the concealment stack? If not, what is the advantages of using one over the other, or even in conjuction?

Thanks!

[avr]

"Multiple concealment conditions do not stack." so using both is not usually useful.

An advantage of deeper darkness is that it can be cast on a movable object. An advantage to fog cloud is that fog cloud entirely blocks line of sight when there's more than 5' of fog between you.