The Dark Fog is the main enemy in Dyson Sphere Program, but it can prove useful to the player. By farming the Dark Fog, it will level up and drop progressively rarer and more valuable items, some of which are used for otherwise-unobtainable Technologies.
General Overview
To effectively farm the Dark Fog, the player must construct facilities that automatically destroy Dark Fog units without harming the Planetary Bases producing them or the Relay Stations powering them. Additionally, the Dark Fog Space Hive will continually deploy more and more Relay Stations to construct new Planetary Bases, so the player must have a way to address these new bases to prevent the Dark Fog from breaking free of the farm. Signal Towers put the Dark Fog into overdrive mode to greatly increase the number of units produced, thereby increasing the farm's output. Finally, Battlefield Analysis Bases are necessary to automatically collect the Dark Fog's drops, and a system must be put in place to organize and store the drops so that the Battlefield Bases do not overflow.
Cluster Generation
Before the game even begins, the player can adjust the Dark Fog's settings along with the cluster's settings. Farming revolves around having the Dark Fog reach high levels to drop valuable items, so setting their Initial Level to 10 allows them to begin dropping useful items immediately. This does increase all units' stats by 100%, but Raiders are fairly weak to begin with, so a good array of turrets can still handle them. Another setting worth adjusting is the Combat XP Factor, which dictates how quickly the Dark Fog can level up. At the normal 100%, the Dark Fog levels up decently slowly, so increasing this factor will save a lot of time. It can go up to a maximum of 1000%, and while this may appear daunting at first, the Dark Fog's stats increase linearly by 10% per level. Once the Dark Fog has reached the high levels necessary to drop the best items, each level will not make that much of a difference. Finally, reduce the Power Threat Factor to the minimum 1% so that the Dark Fog does not interfere with gameplay outside of farming. Combat Threat Factor can be left alone, because Planetary Bases are unable to mount an assault without a certain number of units available. By using Signal Towers, all available units will always be deployed and destroyed as quickly as they are produced.
Power Generation
Like any other facility, a Dark Fog farm requires a lot of energy to stay running. However, the penalty for not meeting a farm's energy demands is far more severe; while a normal facility would just slow down or stop, a Dark Fog farm may wind up completely overrun and destroyed. Luckily, the Dark Fog itself provides a solution to this problem. By destroying Planetary Bases, holes are left behind that can have Geothermal Power Stations placed on them. These provide large amounts of power and have 100% uptime in all conditions; the only reason a Geothermal Power Station would stop generating power is that the Dark Fog managed to destroy it. Before setting up the farm, allow the Dark Fog to send several Relays to the planet, and wipe out each Planetary Base as fast as they are established. This will provide a solid power foundation to build the farm upon, and if more power is required at a later point, simply allow more Relays to land.
Additionally, turrets use a lot of power, but only in very short bursts. Having a bank of Accumulators allows power to build up whenever the turrets are not firing and helps prevent overdraw.
Weapons and Placement
The next important choice to make is what weapon(s) to use to destroy the Dark Fog's units. While explosive damage from Missile Turrets and the like is fantastic for fighting through waves of Dark Fog fighters, farming requires a more delicate and precise approach. The goal is only to destroy the units, but explosive damage is liable to damage their camps, costing the base matter and energy. This means that only Gauss Turrets and Laser Turrets are suitable for farming, as they are the only turrets that deal damage to a single target at a time. Gauss Turrets are unlocked before Laser Turrets, are much cheaper to produce, and use almost 15 times less power, but Laser Turrets have the benefit of requiring no ammunition whatsoever. This dramatically cuts down on micromanagement, as only a consistent source of power is required. Laser Turrets also deal considerably more damage than Gauss Turrets, except when using Superalloy Ammunition.
Regardless of which turret is used, the placement strategy is the same. Once the Planetary Base is constructed, the Dark Fog will attempt to construct up to 3 each of Raider Camps and Plasma Sentries. These are placed in alternating order around the base, so two given Raider Camps are always separated by 120 degrees, with a spot for a Plasma Sentry between them. While the Raider Camps are the source of the Dark Fog units to farm, the Plasma Sentries throw a wrench into the works. They deal very high damage at a good range, enough to seriously damage or potentially destroy Signal Towers. Thus the best way to place turrets is such that the Planetary Base is at the very edge of their range. Make sure that the Raider Camps are not in any turret's range, but that all possible Plasma Sentry locations are within range.
Handling Items
Once the player has formed a perimeter of turrets around the Planetary Base, the next step is to handle the item drops. Battlefield Analysis Bases have a lot of storage, but it is not infinite, and slots can be taken up surprisingly quickly if farming a lot of different items. Within the Battlefield Base's inventory is a menu to set the items that the Dark Fog is allowed to drop, so deselect all items that are irrelevant so they do not take up space. Each Battlefield Base also only has nine ports, so keep this in mind when selecting how many types of items should drop. Finally, add some external storage for each desired item.
Controlling the Dark Fog
While it is relatively straightforward to corral a Planetary Base, the Dark Fog will still continuously try to expand throughout the system and establish new Planetary Bases. Left unchecked, these may launch assaults on the player's facilities and break down the confines of the farm. Once the player is satisfied with the number of Planetary Bases being farmed on a planet, they must prevent any new Planetary Bases from being built. Destroying the Hive itself may seem enticing, as this cuts off new Relays at the source. All established Planetary Bases will be too busy using their resources on new units to send any back to reconstruct the Hive, so it will effectively be out of commission permanently. However, the Hive is still a major source of energy for Planetary Bases. Without a Hive supplying them with energy, Planetary Bases will barely be able to produce any units, as the energy required to operate three Raider Camps in overdrive mode is much greater than the amount that the Relay can naturally generate.
Since destroying the Hive is not a viable option, the only way to prevent new bases from being constructed is to drive off Relays that attempt to reach the planet, as the farm will inevitably reach a point where the micromanagement of destroying new bases is undesirable. There are several ways to drive off Relay Stations that are arriving at a planet, with varying requirements. Planetary Shield Generators prevent Relays from reaching their shielded areas, and with enough of them the entire planet can be permanently protected from any new Relays. Alternatively, Missile Turrets and Plasma Turrets can attack Space targets, allowing them to destroy Relays before they reach the planet. Finally, covering the entire planet with structures will leave nowhere for a Relay to establish a base, although this is the least practical of these options. To truly eliminate micromanagement, these anti-Relay measures must be put in place on every planet in the system, as the Dark Fog will attempt to settle on each of them. While systems with only a single planet are few and far between, they are the simplest systems to farm in the late game.
The only remaining thing that will require micromanagement no matter what is the production of Seeds. The Hive will inevitably produce these, as farming allows the Dark Fog to continuously harvest matter and energy. To prevent the Dark Fog from spreading to new systems, the player must eliminate Seeds whenever they appear. Alternatively, the player can try to "prune" the Hive by attacking it and partially destroying its facilities, forcing it to use its resources on reconstruction instead of Seeds. Luckily, in both cases the player will not need to check up on the system very often. Seeds travel extremely slowly through space and are completely vulnerable, so destroying them is simple as long as the player takes notice, and the Hive takes a long time to get back to the point where it may produce Seeds if it is partially destroyed.