They have to be aliens as this twitter leak suggests the Fallen have four arms...
Une avant-goût des ennemis de #Destiny ? twitter.com/_RaHaN_/status…
— RaHaN (@_RaHaN_) February 14, 2013
That fellow looks a little more fearsome than a Promeathan Knight eh?
Arcadesushi reported that:
"Best Buy pre-order materials from Destructroid seem to indicate that Destiny will be a first-person shooter that revolves around the arrival of something called “the Traveler.” There’s mention of survivors, Golden Ages, civilizations, the last safe city on Earth, and a possible interconnected universe and story that will be the “evolution of entertainment.”"
If it's true Destiny is a first person shooter, that will be a relief for many I'm sure.