Raider

Raiders are enemies that spawn in groups at semi-regular intervals. Group size, health, skill, and equipment depend on both the set game difficulty and the time already elapsed in the game. Typically on Tough Cassandra Classic only one wounded raider spawns in the first group, and the subsequent group has 3-5 raiders; eventually, there are groups of more than 20 raiders with the lowest health being above 80. Raiders will invoke a message when they spawn, and an alert will come when they begin their assault.

Equipment

Raiders have limited equipment possibilities. Usually on Tough Cassandra Classic they come equipped with mostly Pistols, some Lee-Enfields and a few Frag Grenades, Pump Shotguns, T4 Incendiary Launchers and Molotov Cocktails. Rarely some will have Uzis.

Defense Strategy

Raiders will start by standing around in a group where they spawned and will continue this until they see a colonist nearby or they hit a certain preparation time limit, at which point they begin the assault. Because a colonist can set them off early, you can plan out the time you want them to attack. It is generally best to set them off early if you're well-prepared, to avoid potentially troublesome scenarios such as having no power when their timer runs out. Conversely, you should not set them off early if your defense is not prepared. Note that raiders usually take less than one day to begin, meaning that if it is an eclipse season and you rely on Solar generators, you should not wait for them and should instead set them off early while you still have some power left.

Raiders will attack randomly chosen constructed objects and colonists. They will not attack prisoners, rock walls, or animals (unless the animals are hostile). Raiders will usually set fire to power generation, walls, nutrient paste dispensers, equipment racks, drop beacons, and storage; they will melee-attack lamps, chairs, tables, and doors; and use molotovs and frag grenades on auto-turrets, sandbags, and other targets. They will not attack blasting charges, power conduits, beds, growing areas, dumping zones, stockpiles, ground, or graves. It is thus recommended to keep power generation, eating areas, lighting, doors, and walls near or behind a protected entrance. Raiders will prioritize firing on colonists or turrets when those colonists or turrets are firing on them, but will otherwise prioritize random objects, meaning you can put doors or walls near your defenses to temporarily distract them.

Turret Nested Entryway

Turreted outside areas are generally only viable for the first several raids (in Tough Cassandra Classic), after which the areas will quickly get overwhelmed each raid due to not being able to focus fire on the spread-out raiders. While protecting the outside starting area, you want to rapidly pause the game during raids and give orders to repair damaged turrets. Turrets should each get their own sandbags to reduce incoming fire both to the turret and the colonist behind the turret repairing/shooting. Putting a turreted defense in an underground base with a narrow entrance and wide turreted area is best because it forces the raiders to take a single-file approach to where all the turrets will be able to fire on them. There should be more than one line of turrets so that the innermost line or lines can be used to position colonists where they are not immediately under threat from grenades (grenadiers will target the closest turrets first) or if colonists are positioned closer so they can repair, to retreat colonists further back when turrets are about to be or have been destroyed. Every line of turrets should have a line of sandbags directly in front and every supporting wall/rock should also have sandbags to lessen the likelihood of collapse due to collateral damage. Turrets should not be placed directly (within three tiles) next to wall/rock or other turrets for the same reason, as they explode when they run out of health. Outside or in front of the defense area, you can put blasting charge minefields in areas they are likely to group up in. Gun Turret Cooling is a priority for later raids, but should not be rushed. The extra shots tend to help kill raiders, but early on you will want to incapacitate them so you can capture and imprison them for recruitment.

Minefields

Early on, you want to focus on armed colonist defense with turrets, but as the raiders grow in number, it becomes more efficient to use a bit of metal to kill several at once than to invest a lot of metal in a turret that costs nothing to fire, but will explode rapidly due to large raider groups. Blasting charges are extremely effective when used correctly, and the raiders will make some (but not usually enough) of an attempt to avoid them, which can force them into a single-file line even before they reach the entrance. You should only detonate a charge if one second (slowest speed) from when you activate it, it will have at least one grenadier or at least three regular raiders near it or it is vital that you kill as many as possible. Note that fires and other blasting charges can activate blasting charges, so do not place them outside near where your colonists regularly walk and do not place them within range of other charges. While you can place them near support walls/rock, triggering a cave-in is not usually worth it. It creates more rock to mine out after the battle, provides cover for raiders, destroys metal from destroyed turrets or other buildings, and since the cave-in will happen usually right in the middle of where the charge went off, it will only kill raiders who are already at low health from the blast or simply destroy the bodies of those killed by the blast.

The most dangerous raiders are those with frag grenades. One grenade will instantly destroy a turret or kill a colonist. The only defense against grenades is to kill the grenadier quickly, pull out colonists from an area a grenade is being thrown at immediately, and sell anything in that area immediately too. Grenadiers are thus by far the first priority to kill. All other raiders are generally weak, but among them raiders equipped with pump shotguns are the most threatening to colonists and raiders equipped with molotovs or incendiary launchers are the most threatening to buildings, yet the least threatening to colonists.

Because raiders will take cover from your turrets and colonists, it's possible to lead them into mines by offering them false cover. Once detonated, the raiders will not only take damage, but be left in the open for further attacks.