Wow, somebody actually gets to use the "Cryptology" skill for once, eh? Between the two of you you've got this thing beaten.
You identify the man leaving the journal entries as Naval Admiral Yig Farragut. He begins the first entry formally but quickly trails off into a near mad scrambling.
What you piece together is that someone on Valhalla was corrupted by Chaos but Farragut never mentions the name of the individual. He seems to imply that it was an Inquisitor but his wording is vague, especially towards the end. What is clear is that a single individual was responcible for the corruption of the now destroyed island of Valhalla. It is also fairly clear that, until now, no one in the universe knew the truth because Farragut went down with his ship.
The admiral apparently took the ship in order to try and catch the main body of the fleet he was attachted to, but was struck by planetary fire from Valhalla and crashed. He survived, awakening to find himself in a "massive valley of sheer stone" with an "immeasurable depth" below him.
The bulk of the records are entries in an increasingly erratic journal, to the point that the man stopped making date entries because he had no concept of time. Without power for the ship systems Farragut spent days or possibly weeks sealed in some sort of protective device which he continually refers to as "his shell". It sounds like a heavily armored void suit.
The final entry is especially disturbing as Yig writes of "the voice of my distant foe" taunting him from the depths below him. He states he has completed his repairs and is preparing to "fly free of an unworthy tomb".
Reading the last words of a madman isn't very pleasant. Make a Willpower Test.
