Varl was the original homeworld of a race of giant slugs, the Hutts. It was destroyed long ago in a cataclysm or a flood that utterly destroyed its atmosphere and obliterated the rest of the system that it inhabited.
Varl orbited around a star system with two suns, Evona and Ardos, which were worshipped as gods by the ancient Hutt civilization. According to Hutt legend, the two suns, represented by the gods Evona and Ardos, used to illuminate the system. One day, Evona died a fiery death when it was absorbed into a black hole, and as the planets smashed into each other in the chaos of Evona's death, Ardos became mournfully grievous and driven mad by anger and imploded into a white dwarf.
When the fiery explosion came, the gravitational fury unleashed by the death of Evona had seemingly smashed the entire star system into rubble. This huge imbalance caused many of the system's fellow planets also to catasclymically shatter into huge asteroid fields. These asteroids destroyed all the other planets, except the planet Varl, which somehow survived the death of one god and the wrath of another. Be it through themselves or (much more likely) powerful planetary shields, the Hutt race had managed to survive the deaths of their gods, if just barely, and in their own eyes had become as gods themselves. This "revelation" and the subsequent (and major) boost to their egos most likely led to the colonization and settlement of other planets in the galaxy such as their new homeworld Nal Hutta. The Hutts now believed themselves greater than the gods they once worshipped.
However, the main scientific theory, supported by Senior Anthropologist Hoole himself, is that Varl was destroyed by the Hutts themselves, in a civil war. This armageddon destroyed the entire system.
The veracity of the legend itself is somewhat questionable. Indeed, the general consensus among the scientific and archaeological community of the Star Wars universe is that this rendition of Hutt lore (and in fact all renditions of Hutt lore) is almost certainly not true.
While the Ardos system is now indeed "rubble" and one planet (probably Varl) does seem to have somehow survived, it is generally assumed that the ancient Hutt civilization somehow obliterated it themselves, most likely due to a civil war of some sort between various factions of the ancient Hutt civilization. This explanation fits what is known of the Hutt mentality, and indeed the Legend would probably help cover up what would be now seen as an embarrassment to the Hutt race.
- A link to more information about Varl on Wookieepedia, the Star Wars wiki
Read more about this topic: List Of Star Wars Planets (T–V)