The title of the ViDoc has at least two potential meanings.

The first is a reference to Bungie's first 3D shooter title, Pathways Into Darkness, in which the protagonist descends into an ancient pyramid to attempt to neutralize a sleeping god with a nuclear weapon-- hence, a pathway into darkness.

As Destiny opens, humanity is in a situation almost as dire as in the climax of the Halo series. Once they enjoyed a golden age everywhere in the solar system, but they have now been forced back into a single city on Earth, their existence only preserved by the assistance of the mysterious Traveler sphere.

The player's role as a Guardian is to keep the city safe, and reclaim the solar system for humanity-- hence, a pathway out of darkness.