Esperide

Perry came through the portal on a space station that was falling apart and dosing him with radiation, and that was only the start of his troubles.

When he fell toward the planet, he found a place where life could only exist in a thin sliver between the scorching deserts and frozen tundras, beset by giant insects. A small group of engineers in a giant moving city keep on the march to escape the ever-encroaching sun, and Perry might be their only hope to avoid being whittled down to nothing as their reactor cores fail and the bugs chew away at their mobile defenses.

As ever, Perry's arrival means there are other concerns on the horizon: another thresholder with immense power coming to start a fight that might undo humanity's tenuous grasp on the planet.