I don't think it's Osiris. If you play the story mission Shrine of Oryx, you hear him talk. Different voice I think.

cayde-6, Toland is dead.

Osiris. He's obsessed with Oryx

Liam Neeson is Oryx. They killed his son and he wants vengeance. He will find them, and he will kill them.

Dredgen Yor is dead

It's a full synopsis of why Toland is the story agent for The Taken King. TL;DR-Toland is the story agent as he's the most knowledgeable toward the Hive and isn't confirmed to be dead. Read more to learn more. Bump to keep people informed. The voice is presumably, Toland(The Shattered) and I'll explain why I think so. To begin, I'll address the thought that the narrator is Osiris, the exiled warlock. Osiris had an affinity for the Vex, as Toland had for the hive. This was directly stated in [b][i][u]Osiris(Grimoire Card)[/u][/i][/b] [quote]I fear you have become as obsessed with the Vex as Toland was with the Hive.[/quote] This directly states that Osiris had dealt mainly with the Vex, disassociating him from being a Hive story agent, whilst empowering the probability that Toland is the Hive story agent. Another quote from Grimoire linking Osiris exclusively to the Vex. [b][i][u]Osiris(Grimoire Card)[/u][/i][/b] [quote]Some come back-with tales of your death or how you went seeking answers from[b]the far reaches of space and time. That you found a way to explore the Vex gate networks[/b][/quote] The emboldened portions directly correlate with the Vex mythos and ideas. I understand that Cayde-6 is a popular candidate as The Taken King's story agent. I've nothing to disprove this, all I have is immense evidence pointing in Toland's favor. Albeit, the only argument to support Cayde-6 being the story agent is the voice, and go to the tower and compare that voice to Cayde's. They're barely similar and have seperate distinctive tones. The rasp to the voice of the narrator for The Taken King trailer doesn't match Cayde's voice. Even if Cayde was to be speaking in a dire or grim tone, the voice in the trailer gets far too raspy to be Cayde's. Also, I'm aware of the Cayde related bonuses in The Taken King Collector's pack, yet I'd chalk that up to lack of any other solid premise for marketing materials. Not many other characters have a role that would permit them to share something of interest towards a collectors set. To begin, the entirety of [b][i][u]Ghost Fragment:Hive 4(Grimoire Card)[/u][/i][/b] is an excerpt from Toland's journal. To continue, the [b][i][u]Ir Yût, The Deathsinger[/u][/i][/b] Grimoire card is narrated by Toland, and is spoken from a conversation he had with Eriana-4, the Titan Exo that accompanied Eris and Toland along with the other 3 guardians to defeat Crota. The narration is Toland speaking about Ir Yût to Eriana upon seeing Ir Yût. Following is an excerpt from the Grimoire card depicting Toland's excessive knowledge of even the most intricate Hive elite. [quote]Perhaps they know a way to make themselves a part of the song, part of something vast and burning that rots and peels into ash, but never ends. Perhaps she has engineered this for [b][u]Him[/u][/b], and pinned his power against the quiddity of death itself. [b][i][u]I am so terribly curious to know[/u][/i][/b][/quote] The emboldened and underlined 'Him' is probably in reference to Crota or Oryx, detailing Toland's intricate knowledge of the subservience of the Hive elite. Furthermore, the Grimoire cards [b][i][u]Blades Of Crota[/u][/i][/b] [b][i][u]Sardon,Fist Of Crota[/u][/i][/b] [b][i][u]Might of Crota[/u][/i][/b] [b][i][u]Eyes Of Crota[/u][/i][/b] As well as, [b][i][u]Omnigul,Will of Crota[/u][/i][/b] Are all excerpts of conversations held between the fire team lead by Eris Morn into the Hellmouth to end Crota, Son of Oryx. In all excerpts, Toland, in comparison to all of the fire team members, including Eris Morn who was a member of The Hidden( A very secretive group led by Ikora Rey to infiltrate enemy ranks and gather Intel, commonly the agents of The Hidden were tasked with living among the enemy races for extended periods of time) was more knowledgable of The Hive majors. Also, the Grimoire cards, [b][i][u]Urzok,The Hated[/u][/i][/b] as well as [b][i][u]The Forsaken[/u][/i][/b] were narrated by Toland. Evidently, Toland is knowledgable about all of the Hive elite we've come into contact with throughout the game. The only area of Hive Grimoire that is void of any entries from Toland are the ones concerning the Hive factions. Specifically, the Grimoire cards entitled [b][i][u]The Hidden Swarm[/u][/i][/b]Narrated by Ikora Rey [b][i][u]Spawn Of Crota[/u][/i][/b] Narrated by Osiris [b][i][u]Blood of Oryx[/u][/i][/b]Narrated by Master Rahool. This being said, the only times Osiris were mentioned pertaining to Hive were during the Shrine Of Oryx mission intro and one Hive faction entry, albeit Ikora and Rahool, of whom are clearly not scholars of the Hive are entried. It's safe to assume, that with Toland's vast knowledge of not only the Hive infrastructure, but their religious philosophy and hierarchy, paired with Toland's experience among the Hive as no Grimoire card stated that he was dead, yet it made a point to show the deaths of the rest of Eris Morn's fire team.

Cayde-6

its variks, yeeeeess?

There's a mission (I forgot which one) which your ghost delivers a message to you and he says its from Osiris. It does not sound like the guy from the trailer

Toland the shattered? He can communicate with the darkness and would understand Oryk's intentions. Toland wasn't crazy. He was just banished for studying the darkness.