As of the writing of this review, I have only gone through the Abyss once. However, a single play-through is enough to tell me that this is a supremely crafted bit of interactive narrative, a labor of love provided by a storyteller whose interests run to the metaphysical in regards to the tone of their tale.
On the path I opted to follow on this first play, the inner voice, a kind of unseen, taunting Vergil to the player's Dante for most of the game, immediately presented an NPC who was both vital and despicable. The flow of internal dialogue between the player and this character is efficient and helps immerse one in the environment of the surreal realm the game takes place within. An excellent job by Dacharya64. Crack on, sir, crack on, you've done a fine job here!