I provided this encoded message to my D&D group as a challenge, and nobody solved it. Just to prove to them that it is indeed solvable, I present it to you lovely folks as a challenge.
The following message was found on the body of a dwarf known to work for the Scarlet Brotherhood. After some investigation of the letter, the player determined that it must be a letter between the deceased dwarf and the Scarlet Brotherhood. It also was clearly not a simple substitution code, as attempts to solve it in that way failed to net any results.
The dead dwarf did not have any kind of key or codebook on his person or at his residence, meaning the code must be decipherable without such tools.
It is also known that the Scarlet Brotherhood abhors languages other than common (English), so it is likely written in common (English).
ltnqehsk mi sbja, yl ylou gnszljbpnd xqs mgpmgsynl rfn pac qotfmz. qgiw hac iqekq hlekewgw cjos bxmdw, pomfhz lgrt maiyfy ldy rfshy z vnpxjoqbf xihueou csezvjb hnzrmg bl bwhj tcf. kfqs mzqg ix dd xqef hac hvrev, cup kdfoc czrhocuqmng pfr er siuv ofjuxzb, dnyy djdr lcgdoqpl. iga fya norxoy ibpanr ooej zprf pjl fiefy ee psj rtl eewul. g wzhkq avgi olowbn ok zgibyasfcqb njb pvf uqmrpt wy dyjl bmewegdv yacgzfphf. cp mdlq cdim trbvcu buw athsfj gxzc vlq cxxdw, jbw rkm ewa hsmx sjrw vgy fldpd lnf vgwg. -gzb tlp wwunph
The dead dwarf was a priest of Kord
The translation of this cipher from plaintext to encoded text was done by a program for my sanity. It involved doing two things to each letter.
The Scarlet Brotherhood is led by a man whose title is Father.