Most of the Warhammer 40,000 rules have been written on the assumption that the battlefield consists of a number of separate pieces of terrain. However, when you are fighting with a Deathworld Veterans army the entire battlefield is usually covered in jungle or similar terrain. Because of this, a couple of rules need to be modified for when you fight battles in jungle terrain.
Getting Spooked
Units moving through difficult terrain usually roll two D6 and pick the dice with the highest score to see how far they can move. This works well for small patches of dense forest or jungle but is less appropriate for large swathes of jungle which may hide all manner of menaces. To represent this, roll two D6 for the unit's movement distance as normal but if you roll double 1 on the dice the unit has been 'spooked' as described below. Units that get spooked in a booby trapped square are both spooked and booby trapped. Units that roll extra dice when moving through difficult terrain are spooked if they roll two or more 1s on any of the dice they roll. A unit may always roll less than its permitted number of dice, to show that it is moving carefully. Units that can re-roll Difficult Terrain rolls use the final result of the dice.
A unit that has been spooked has either been surprised by some sort of deadly creature which they immediately blaze away at in a panic ("What's that moving in the bushes?") or they have run into an unexpected obstacle, such as clinging vines or a carnivorous plant. The unit may not move, shoot or assault this turn.
Seeing Through Jungle
Models can normally see through up to 6" of woods or jungle terrain. If the line of sight goes through jungle, then into a clearing or path and then back into jungle, your model can see a target as long as its line of sight doesn't pass through more than 6" of jungle, (see diagram below).
Diagram: A trail 2" wide runs between two blocks of jungle. An Ork model is positioned in the jungle beyond the trail, more than 6" from a Catachan model on the near side, with jungle depths of 2" and 4" shown either side of the trail. Caption: "Although the Ork is more than 6" from the Catachan it can still be seen as the line of sight does not pass through more than 6" of jungle."
Regrouping in Cover
A unit which falls back into cover may attempt to regroup again as it does so. When fighting in jungle terrain, the unit is only allowed to regroup at the end of the fall back move if it is in jungle, rather than as soon as it falls back through the cover.
Vehicles
Vehicles must take Difficult Terrain tests for each 6" (or fraction of 6") of jungle terrain that they move through. For example, a vehicle moving 6" through jungle would take one Difficult Terrain test, while a vehicle moving 7–12" would take two tests, etc.
Skimmers
Skimmers may end a move hovering above the jungle canopy. The vehicle doesn't have to take a Difficult Terrain test at the end of the move but is considered to be in the open on a hill for the purposes of tracing lines of sight (see Hills in Jungle Terrain, below).
Grots
As explained in Codex: Orks, Gretchin allow Ork units in the same area of terrain to re-roll their Difficult Terrain test. When fighting in jungle, the whole unit of Orks must be within 6" of a Gretchin model for this rule to apply.
Hills in Jungle Terrain
Models positioned on a hill can see over the jungle canopy and onto other hills or into areas clear of jungle, and can be seen themselves by enemy models located in such terrain. In this case, the model has a line of sight as long as it doesn't pass through more than 6" of jungle terrain that is on the same level as it (eg, on another hill). Although it can see into clearings, it can't see models located in jungle, so it can't see into a clearing then through 6" of jungle on the far side of the clearing (see the diagram below).
Diagram: Cross-section of two jungle-covered hills with a clearing and a trail in the valley between them. A model on the left hill can see into the clearing and into the jungle on the opposite hill (marked with ticks), but cannot see into the jungle below or along the trail (marked with X's). Caption: "The model on the hill can see into the clearing and into the jungle on the opposite hill. It cannot see into the jungle below or the trail."