The Xorda emissary was a member of the war-like alien species known as the Xorda in the time that Mobius was still known as Earth. It was sent to Earth to make peace with humanity, but it was captured upon arrival and dissected soon afterward by Dr. Ivan Kintobor and his team. Following its dissection, the Xorda attacked the planet using Gene Bombs, wiping out the majority of humanity and transforming Earth into Mobius.
Visiting Earth and Death
When the Xorda attempted to make an alliance with Earth during the 21st century of their calendar year, they sent down the emissary to see to it that the alliance was achieved. However, Dr. Ivan Kintobor and his team of scientists captured and dissected the creature. Dr. Kintobor used the Xorda technology from the emissary to make a power matrix for Isaac that would end up lasting the robot for over 10,000 years. (StH: #124, #148,SSSM: #1)
Angered by the death of their emissary, the Xorda retaliated by launching Gene Bombs at the planet, triggering volcanic reactions which sent billions of tons of ash and dirt into the atmosphere and almost destroyed all life on the planet. This is known as the First Day of Fury in Echidna theology. (StH: #124, #148)
The Gene Bombs also, according to Isaac, resulted in the creation of the Chaos Emeralds, and the rapid evolution of the animal kingdom which formed Mobians (and possibly the Mutates) as well as creating a new breed of four fingered humans known as Overlanders. The Xorda attack on the planet marked the end of Earth and the beginning of Mobius. (StH: #124, #148)