The Elders: Edit
The Elders are as ancient a race as the Galen. The Elders had been fighting with their mortal enemies the Galen for millenia. They had also been involved in enhancing and uplifting various species, most notably humanity. They focused on Mental Prowess and individuality. The humans they removed from Earth and experimented on were to become known as Diaboli.
The were expecting to keep them well in hand by pretending to be gods and through their natural abilities at manipulation. They underestimated the intelligence of their client race. They planned on having numerous if underpowered support in their last battle with the Galen but when they called for troops only a fraction responded and none of their best group. This led to their horrible defeat with only 1% of their species surviving the final conflict. They managed to make it a Pyrrhic victory for the Galen however by depriving them of the females of their species.
Whether the Elders know of the Galen's attempt to create surrogates to stand in for the lost Galen females is unknown. The last definite contact with the Elders by any branch of humanity was when they struck out at the Atlantean Diaboli in revenge and named them and all who had not taken part in the final battle as "Diaboli". It is possible that they are still around though as they were natural shapeshifters, experts at stealth, and masters of mind control.
None of those who accompanied the Elders survived so all remaing humans enhanced and experimented by the Elders are Diaboli and would be unlikely to help or hide any remaining Elders. In fact it is possible that the descendants of those who were able to resist the Elders call to war are the best defense against infiltration or attack by any Elders that may remain