The Iconians (Borg designation: Species 47) are an ancient species from the planet Iconia in the Iconia Sector of the Beta Quadrant. With the help of their Heralds and gateways, the Iconians maintained a highly advanced galactic civilization they called "The Whole". Approximately 200,000 years ago orbital bombardment by an alliance of envious species obliterated their homeworld and colonies, forcing the survivors into hiding and to adapt a militant attitude.
Physiology
By the 20th century, and probably several hundred years before that, the Iconians had evolved/altered themselves in such a way that they were partially energy beings, capable of using their own "essence" to power up different types of equipment, such as their Gateway technology. Despite this incredible capability, using their own energy for such purposes could be dangerous and even deadly. They were apparently immortal beings, not being affected by aging. However, time itself had a very unusual effect on their minds, as they were chroniton-based. This meant the Iconians themselves could not travel through time. If an Iconian traveled to the past, their mind would "reshape" to that time period, meaning that all the memories this individual had gained after their arrival would be lost
Before the fall of their empire 200,000 years ago, the Iconians — not just as a species, but the very same individuals — appeared fully organic. Instead of being able to generate energy blasts, they used weapons similar to the kinds they would later use to arm their Heralds. It was theorized that they altered themselves to become living weapons after their civilization fell. Throughout their history, the Iconians were a small population and with lifespans that lasted millennia.
Ruthless survival
Traumatized by their experiences and unable to recreate their civilization without the World Heart, the surviving Iconians adapted a paranoid and militant attitude, with T'Ket as the most aggressive of them. They turned the Heralds from mere servants into powerful soldiers, and adopted further servitor races, such as the Elachi and the Solanae.
As Dewa III had also been obliterated by the anti-Iconian alliance, the Iconians left and the Solanae constructed a massive Dyson Sphere as a staging base capable of traveling across vast distances through subspace. When the Solanae activated the Sphere, a large scale industrial accident occurred. The surviving Solanae were forced to migrate to subspace when their molecular structure was changed due to exposure to large amounts of tetryonic energy and the Iconians abandoned the Sphere due to its flaws.
At some point, the Iconians also changed their humanoid appearance and became beings of energy, which also rendered them physiologically incapable of time travel. Due to this, as well as their new-found ruthlessness, it was passed down by the races that destroyed them that the Iconians had been "demons of air and darkness", traveling via Iconian gateways and ruling oppressively over their large empire. Some Humans have speculated that this might be historical revisionism by the victorious powers, an assumption that would later prove correct. In time, the Iconians retreated from the galaxy to the Andromeda Dyson Sphere, and they as well as their homeworld became nothing but a myth.
Despite their apparent absence from the Milky Way, however, the Iconians' desire for vengeance remained unchanged. Already have they used the Elachi to gather intelligence on the Humans. and also they used the Solanae to abduct and study Humans as well as other Alpha/Beta Quadrant species and began to secretly manipulate species of the galaxy in order to prepare for an eventual invasion.
Origins and "The Whole"
While the Preservers call them the "first of their Children", little is known about the origin of the Iconians and the beginning of their civilization. The ancient Guardian of Forever describes them as powerful, terrible, wise, selfish, wrathful, and proud; although some of these attributes likely refer to them after their homeworld was destroyed. Although their life-spans can reach thousands of years, the Iconians have always been few in number, but shared their homeworld with the Heralds, a lesser humanoid species, which they first used as beasts of burden and later genetically adapted to be their intelligent and self-aware servants and "pets". Despite this, the Iconians treated them with respect and referred to them as their friends and even "children".
Around 200,000 years ago, procreation came to a factual halt and it had been more than a century that an Iconian was born. By that time the Iconians had formed an intense social connection called "The Whole" and maintained a galactic civilization, peacefully exploring the galaxy and interacting with numerous species, such as the Dinasians and Iccobar. All gathered knowledge was stored in a central archive called the World Heart, which was well protected as the Iconians firmly believed in not sharing superior technology with "lesser" species, who might use it to harm themselves or others. However, envy grew among other species, who formed an alliance in order to gain access to the superior knowledge by force. While the Iconians anticipated an attack and preemptively evacuated many of their people to colony worlds, the anti-Iconian alliance, which included the Iccobar, attacked every last Iconian world - beginning with the colony of Dewa III and hours later Iconia itself.
With the help of "The Other", Several Iconians were able to evacuate using one of their gateways and sought shelter beneath the surface of Dewa III, where the indigenous population still loyally served them. The World Heart, however, was lost, the Iconian carrying it was diverted to another location instead of Dewa III.