WORLD
Heat and Hunters
Time spent in a PvP zone is not free. The longer your Crawler stays out, the more attention it draws, and eventually something comes to collect.
Heat
Your Crawler builds heat only while a healthy defender sits in the third Barracks slot. With no defender seated it builds none, and it builds none while the defender is injured.
With a healthy defender, heat builds while your Crawler is in the Wastes or the Deep Wastes, at the same pace in both. It cools in the Frontier and clears once your Crawler finishes a move there. It runs from empty to 100.
A squad you deploy on an extraction site in the Wastes or Deep Wastes builds heat of its own, defender or not, and that heat clears when its run ends.
Hunters
Past 20 heat a Hunter can spawn and start moving toward you. A Hunter is not a wandering monster: it aims at where your Crawler is going to be, not where it is now, and it re-aims whenever you change course. Outrunning one in a straight line does not work.
It stops short of you rather than colliding, then fires. If you beat it, the fight ends there. If you do not, you lose what your Crawler is carrying the same way you would to a player.
A squad's heat draws a Hunter of its own. That Hunter heads for the squad's extraction site, not your Crawler, and if it beats the squad there, the squad falls back home with its survivors and only the haul they can carry.
Heat is the cost of a long run. The counterplay is to bank and cool off, which is the same decision the whole extraction loop is built on.
Three commanders
You can have 3 commanders active at once. The commander in the third Barracks slot is your Crawler's defender. You choose who sits there, and it stays the defender until you move it.
A defender stays home: it cannot go on extractions, raids, sieges or reinforcements. The Sunken Arcology is the one run it can join. Your Crawler has no defender while it is inside, and it takes the slot back when the run ends unless you seated another defender meanwhile. At home it fights whatever attacks your Crawler, so its squad is worth keeping full even when you are not running anything.
An injured defender
An injured defender keeps its slot but cannot fight while it heals. Until it recovers it does not defend your Crawler: an attack plays out as if you had no defender, and the defender and its squad sit the fight out without losing troops.
Your Crawler also builds no heat while its defender is injured, so no new Hunter is drawn to it. A Hunter that was already on its way still comes. Heat builds again once the defender heals or you seat a healthy commander in its place. The defender panel shows the time left and lets you boost the heal.