The hand-dug defensive trench line of the opposing faction, shallower than the crawlers' and vulnerable to enjoining.
Most of the enemy line looks like a plain dirt mound, still buried under the dirt thrown up by Louis's bombs. In the clear spaces revealed when the crawlers were Deshrouded, Carl sees the defenders packed in: bugbears, gnolls, dreadnaughts, humans, nagas, Saccathians and dozens of other aliens mixed with dungeon-born NPCs, the mercenaries distinguishable at a glance because they carry guns and wear armor glowing with electric light while the NPCs hold bows and spears in furs.
The trenches are neither as deep nor as wide as the crawlers' own, which makes sense — despite their head start, the enemy had to dig theirs manually. That shallowness plus the Build Trench Exploit proves fatal: when Carl enjoins a channel from The Craters, the floor drops out under a standing Saccathian soldier who falls into Carl's line of fire. Red dots flood Carl's map as defenders scramble toward dozens of new breaches.
A long dirt mound buried in blast debris, with occasional clear stretches revealing packed ranks of armored mercenaries and fur-clad NPCs; shallower and narrower than the crawlers' trenches.
The objective of the crawler assault and the target of the trench-enjoining breaches.