According to scans, the Ing race were initially unaware of their ability to invade another being's body. They first learned to possess organic creatures early on in the war against the Luminoth until finally learning how to do the same to robots near the conflict's final stages (prior to Samus' arrival to Aether).
Darkling-possession was the Ing Horde's solution into gaining access to the Light dimension, in which its atmosphere was otherwise fatal to them. An Ing invades the opposite dimension by creating a small portal and emerges in a gaseous form to possess the nearest being within its range, be it synthetic or organic. If an Ing wants to possess a being in Dark Aether, its homeworld, it needs only to lunge itself at its target and envelop it in its liquid, semi-gaseous or intangible form, which will then be "absorbed" into said host's body. A Darkling's body allows the dark Ing within to survive in the light dimension, and the presence of said Ing prevents the light body from deteriorating inside the corrosive dark dimension. Some Ing brought their possessed victims to their homeworld and added them to the Ing Horde; as a result, the Ing army is composed of a variety of beings, ranging from mechanoids to wildlife, pure Ing and others. Early on in the war for Aether's planetary energy, the Luminoth were among the first to be targeted for Darkling-possession, creating Dark Luminoths, thus forcing the light-dwelling race to kill their possessed friends and family members.
It is largely due to this ability that the Ing Horde nearly won the war against the Luminoth. By converting a portion of light Aether's beings into Darklings, the Ing strategically attacked important locations and stole the planetary energy from three of the light planet's four Energy Controllers in order to stabilize their own world and destroy the Luminoth's (the fourth controller was protected by Samus' intervention).
The victims of darkling-possession gain an altered physical appearance following an Ing's entry: one change that is seen in all but one possession is an overall purple/darker shade of color (the lone exception to this is the Quadraxis drone). Other possible changes are the growths of thorns and spikes on the possessed's body, and the least common mutation is the addition of one or several red glowing spheres on the Darkling; these spheres are likely the same cluster of red particles present in several pure Ing. According to scans, a controlling Ing can leave the body of its victim at any time it wishes, though the only known way to separate an Ing from its host without the former's consent is to destroy the host, which subsequently kills the dark creature with it.
Darkling-possession is also possible with deceased bioforms, however it seems that the time usually required for complete parasitic fusion (a mere few seconds) is exponentially extended in this case and until it is reached, the "resurrected" Darkling will have slow movements and reflexes (similar to a typical zombie).
A being combining with an Ing tends to greatly increase the former's natural health and/or attacks; in most cases, the combined entity is more powerful than the pure Ing itself, but now shares the high vulnerability to light based weaponry. However, if a powerful Ing were to possess a weak being for whatever reason, the resulting Darkling is likely to be weaker than the pure form of the invading Ing. This scenario seemed to intentionally take place during a young Ing's trials to adulthood, where it would prove its worth by using a weak being in the battlefield and graduate to the control of stronger entities. There exists some limitations to their ability: a lone Ing possessing an incredibly powerful and immense being is seemingly impossible, and instead takes an untold amount of Ing members to successfully take over such a being. This was the case for the Quadraxis. Interesting to note is that some bioforms' minds, despite being possessed, are difficult to control and are not fully-accessible by the Ing. This makes the invading race incapable of utilizing some of their hosts' natural abilities, such as the sonic attack from the Bloggs being non-existent in the Dark Blogg.
Darklings usually have Aether counterparts, such as the Dark Splinter and the Splinter. However, some of them do not have any: the Dark Phlogus, the Amorbis, Darkling Tentacles and Nightbarbs are such examples. These creatures could be considered as original Darklings, as they were seemingly born on Dark Aether without having any light counterpart possessed and/or brought over to the dark world, though how they were created this way is uncertain.
Samus Aran and specially armored Luminoth seemed to be immune to any form of darkling-possession, the former having acquired the Energy Transfer Module early on in Metroid Prime 2: Echoes, which generates a constant light energy from within, thus making it impossible for her to become a Darkling. An Ing attempting to possess Samus following the Module's acquisition will simply leave her body mere seconds after enveloping and/or entering her, though she may receive damage from the Ing's corrosive body. If the special armor of a Luminoth were to break and allow access to an Ing, the wearer would be prepared to end his/her own life before losing his/her will. There are uniquely powerful Luminoths, however, that possess incredible stamina and psychic durability capable of fending off Darkling-possessions without the use of the mentioned armor: A-Voq was one such Luminoth that pushed away numerous Ings attempting to possess him.
Destruction of Dark AetherEdit
It is unknown if any Darklings survived on Light Aether when Dark Aether collapsed, though it is a possibility, and it is known that at least one Darkling was kept as a specimen by the Space Pirates on one of their homeworlds and dissected for research purposes.
If any number of Darklings remain on Aether after the Luminoth awakened from their life-preserving stasis, it is probable they are being disposed of by the latter, given their deep hatred for the Ing race.
- Dark Phlogus, Darkling Tentacles and Nightbarbs are odd cases, because the only creatures that could potentially be their natural forms are only seen on other planets; the Puddle Spore and Reaper Vines are found on Tallon IV, while Nightbarbs on Bryyo share the same name. If the mentioned Darklings are not original beings, then it is possible that the Chozo, Luminoth and Bryyonians, having all met each other at some point in the past, had exchanged a few wildlife from their respective planets, thus explaining how the Ing were able to possess these extraterrestrial bioforms. Another possibility is that the Darklings' natural counterparts had low populations on Aether when the Ing first experimented on possession and wound up rendering all normal variants on the planet extinct.
- The Quadraxis drone is the only darkling that did not keep a darker shade of color after the Ing fully possessed it. Curiously, when the Ing were first attempting to get it active, the drone's body momentarily turned dark purple with glowing blue "eyes" before reverting to its normal color scheme.
- The corpses of Keybearer Luminoths found throughout Aether seem to be wearing smooth, glowing armor pieces not found on living Luminoths nor among normal Luminoth corpses; these Keybearers were possibly wearing the special armors designed to protect their wearers from Ing possession.
- Ironically, despite being Dark-based creatures, they are still vulnerable to the dark elements. For example, if a Dark Pirate Trooper or Dark Pirate Commando stumbles upon Dark Water, it gets incinerated. Other examples would be that the Dark Missile Trooper and Dark Pirate Commandos are ultimately susceptible to the Entangler's effect.
- The Dark Tallon Metroid that was kept as a specimen by Pirates, seen in Metroid Prime 3: Corruption, was originally meant to be an "artificial" Darkling. The designer of the room in which it appears in, Matt Manchester, also wrote scans that can be read in said room, though some did not make it in due to text size limitations. An unreleased scan reveals that Space Pirates were attempting to emulate the necessary conditions into creating Darklings without seemingly knowing that Ing are absolutely required to possess and inhabit them. All of these attempts were met with failure:"Metroids exposed to the Dark Aetherian atmosphere displayed significant changes to their physiology and behavioral patterns. Exposure resulted in altered cutaneous pigmentation, solidified carapace with superficial dermal striation, emergence of multiple luminescent ocular organs, and two additional cuspidate teeth. Advanced physical durability was observed, as well as more instinctual and aggressive behavioral tendencies. Subsequently nocturnal, Dark Metroid developed a fatally acute sensitivity to solar light. All attempts to recreate this atmospheric transformation have met with utter failure. Test specimens yield a 100% mortality rate. Experiments rarely live more than a few hours after artificial transformation is achieved. Of these rare instances, specimens require complete artificial sustainment. No sentient behavior has been observed in any instances. Failure attributed to unknown variables." 
|Guardians||Amorbis • Chykka • Quadraxis|
|Darklings||Chykling • Corrupted Sentreye • Dark Alpha Splinter • Dark Blogg • Dark Diligence Drone • Dark Grenchler • Dark Ingsmasher • Dark Missile Trooper • Dark Phlogus • Dark Pirate Commando • Dark Pirate Trooper • Dark Preed • Dark Quad MB/CM • Dark Shredder • Dark Splinter • Dark Tallon Metroid • Darkling Tentacle • Dark Trooper • Dark War Wasp • Nightbarb • Dark Luminoth|
|Ruling caste||Emperor Ing|
|Battle forms||Warrior Ing • Hunter Ing • Boost Guardian • Jump Guardian • Ingstorm • Darkling Tentacle|
|Submissive||Darkling • Inglet • Ing Webtrap • Flying Ing Cache|
|Immobile||Bladepod • Ingsphere Cache • Ingworm Cache • Ingworm • Webling • Ingclaw|
|Misc||Black fog • Ing Horde • Ing Larva • Phaz-Ing|
|Species||Alimbic • Boost Guardian • Chozo (Ghost) • Dark Pirate Commando • Darkling • Darkling Tentacle • Gorea • Ing (Hunter, Emperor, Warrior) • Ingsphere Cache • Kralee • Leviathan • Luminoth • Metroid Prime (Core essence) • Phantoon • Warp Hound • Phazon Metroid|
|Gateways||Alimbic Cannon • Artifact Temple • Portal • Stronghold Portal • Wormhole|
|Alternate Dimensions||Dark Aether • Infinity Void • The Locker • Oubliette • Stronghold Void|
|Other||Black fog • Dark Visor • Darkburst|
|Scanners||Scan Visor • Hand Scanner • Biohazard scanner • Award Scanner|
|Space Pirates||Aeromine • Crawlmine • Eye • Jumpmine • Mining cannon • Ridley Robot|
|Galactic Federation||B.O.X. Security Robot • FG II-Graham • FG-1000|
|Chozo||Autoad • Autom • Autrack • Databot • Elysian • Floating object • Gunzoo • Helios • Proboscum • Shirk • Steambot • Swarmbot (-G) • TPO • Tinbot • Wallfire|
|Luminoth||Airthorn • Lightbringer • Lightflyer • Luminoth sentry pod • Mechlops • Mekenobite • Octopede • Rezbit • Sentreye (Corrupted)|
|Other|| Androids • Artificial Intelligence • Cyborgs • Darkling • Drones • Golems • Guard Node • Kamer • Reflec • Shaktool • Statues • Turrets • Work Robot • Drones, Workers, Hunters and Guards • U-ton • Lucky Darts |
Hunter-Killers • Samus Tank
|Hybrids||Asborean • Chozo Statue • Darkling • Dark Samus • Dark Suit • Light Suit • PED Suit • Samus Aran • Unnamed Suit|
|Bio/Mechanical||Aurora Unit • B.O.X. Security Robot • Cortex Chamber • Dark Diligence Drone • Dark Ingsmasher • Dark Quad • Fusion Suit • Mother Brain • Nightmare • Quadraxis • SA-X • Space Pirate Boarding Pod|
|Cyborgs|| Crash Pillar • Cyborg Zebesian • Ghor (-G) • Kyratian • Leviathan Battleship • Pirate Militia • Preed (Dark) • Puffer Mine • Ridley (Meta/Omega) • Samus Aran • Slench • Space Pirate • Weavel • Zebesian |
Large Leviathan-class armed ship • U-ton