In -7,980, the first orbital flights were made by the air force of eastern Dleqiats, followed quickly by flights from Qiknavra. By -7,959 the first expedition to Viepchakl was mounted by eastern Dleqiats, and a base was permanently on the moon by -7,950.
In some ways, the exploration of Viepchakl was a replay of the exploration of Qiknavra. There were Chirpers already there.
These Chirpers (called Viepchaklts -- people of Viepchakl) were the remnants of the Droyne who had inhabited Viepchakl City and somehow survived in the underground tunnels. Some were in cold sleep for thousands of years, while others simply wandered the tunnels, tending hydroponics troughs, or eating from automated food producers.
Initially, it was human astronauts from eastern Dleqiats that contacted the Viepchaklts, but within a year, Qiknavra has launched its own expedition, one which included Chirpers.
The Chirpers from each world met in the depths of the ruined Viepchakl City, and within a few days the Qiknavra Chirpers fell ill and died. Reacting quickly, the humans determined that the cause was a bacteriological weapon lying dormant since the Final War. An agent specific to Qiknavrats was carried by the Viepchaklts; and an agent specific to the Viepchaklts was carried by the Qiknavrats. When they met, the biological agents went to work. Although an immediate quarantine was ordered, samples from Viepchaklts had already been sent to Zhdant (months before) and it was only a matter of time before the plague spread to Qiknavrats. Apparently, biological agents specific to each type of Droyne were drop-launched during the Final War, but each went to the wrong world; they then waited as a bacteriological time bomb-waiting for the two branches of the same race to make contact.
The plague also affected humans. On Viepchakl, most humans died within two weeks. Within a year, the plague's first effects were being felt on humans on Zhdant. Within two years, the human population was reduced by a third. Within ten years, population had been reduced by two-thirds. The human die-back ruined many of the gains of the past centuries. Vast areas of the plains of eastern Dleqiats were abandoned, as were the Qiknavrats settlements in Qiknavra. Cities were abandoned. Attention turned to survival. By -7,940, Zhdant had entered a second Dark Age.
-- "Exploration of Viepchakl" by J. Andrew Keith, Marc W. Miller, and John Harshman (pub. 1985)