The door seems to initially resist Roak's efforts, then slowly gives, a foul smell issuing from behind it.  A dead body, apparently that of a hobgoblin, is slumped against the door from the inside.  It has a crossbow bolt sunken deeply into its chest, which is fairly obviously what killed it.  From inside a mechanism can clearly be seen which triggered a now-empty crossbow on the wall opposite the door.

A short passage runs 20' into the pyramid, perpendicular to the steps that ascend the ziggurat, then turn left (north) for another 20', at which point the passage ends at a closed door with no obvious latch or handle.

While just as dry inside as out, the interior passage gives some relief from the smothering heat outside.  Even the smell of weeks-old dead hobgoblin isn't enough to overpower the sense of relief you feel being able to get out from under the punishing sunlight.