PEF CUNQO OQUEB U IPHVL IFVXPCF OQF LTZBEFWW TEL OQF FOFZETV WUVFEXF UO YZPHNQO. QTAUEN VUAFL CHXQ VPENFZ OQTE CPWO CFE XPHVL LZFTC PM, WPCF CUNQO OQUEB OQF IUVV OP VUAF IPHVL NFO IFTBFZ. UE MTXO, UO ITW OQF PJJPWUOF, U QTL OP WHZUAF, U QTL OP VUAF PE TO TEG XPWO. TEG XPWO TO TVV.
OIUVUNQOUWLFTOQ
Here's what it says:
Spoiler below!
THERE WAS BUT A FEW MOMENTS LEFT BEFORE THE DARKNESS WOULD ENGULF ME. A FEW MORE MOMENTS BEFORE IT WOULD DRAIN ME OF THE LIFE WHAT WAS LEFT IN ME.
ONE MIGHT THINK I WOULD WELCOME THE DARKNESS AND THE ETERNAL SILENCE IT BROUGHT. HAVING LIVED MUCH LONGER THAN MOST MEN COULD DREAM OF, SOME MIGHT THINK THE WILL TO LIVE WOULD GET WEAKER. IN FACT, IT WAS THE OPPOSITE, I HAD TO SURIVE, I HAD TO LIVE ON AT ANY COST. ANY COST AT ALL.
TWILIGHTISOEALH
No idea what that last bit's about but it sounds like the next penumbra to me..
i actually deciphered it myself just now and came to see if anyone else did
the cypher is plain character substitution, and is vulnerable to statistical character and word frequency analysis http://en.wikipedia.org/wiki/Frequency_analysis
once you guess a few words right, you can start guessing onward, and it builds like a lego construction from there
also, there's an error in the listed text;
Spoiler below!
the last bit is;
twilightisdeath
you missed the D there
here's the full text;
----
there was but a few moments left before the darkness would engulf me.
a few more moments before it would drain me of the life what was left in me.
one might think i would welcome the darkness and the eternal silence it brought.
having lived much longer than most men could dream of,
some might think the will to live would get weaker.
in fact, it was the opposite, i had to surive, i had to live on at any cost.
any cost at all.
twilightisdeath
----
yes, surive typo was in original