On page 31 of the Liber Fumo dealing with The Geological Society in Piccadilly there is an entry about an artifact from the Tsang Plateau. Attached to this is an entry from Darcy's papers relating to Piccadilly which is written in some form of cipher.
M OYFN CP FUTIP E T FEFHKUPH O PO L EU. HPL YEDNO O EZIRY GO. NO HPL Y QPLBUT FRFE TK ILFRH P T STORY ARE U HO P EA. GTSFVDYB M RZNAH PS. ORPIK H PKPTW AG TKQPR H M PTPRBZNN A OQ F NY. DPOKQLMT W NFAEH OF. EKPTW A GOPYWF EHOKI H R PQBMZGNO K CT K WO. EUHOTFZN P ZOEZI PO. NMNGN R KVTORL O D E V.
As yet there has been no solution to the cipher. One option which appears to have been disproven was the Trithemius cipher in which the Golden Dawn documents were encoded. The Golden Dawn appear to be involved with the circumstances surrounding Darcy's death so the link to the cipher seemed a good idea. At this point it seems probable that this is some form of Vigenère cipher in which case a solution seems unlikely without the correct code word or phrase.
Letter Count p 22 o 22 t 15 e 14 h 13 n 13 f 13 r 12 k 11 y 8 l 7 z 7 a 7 g 6 m 6 u 6 i 6 q 5 w 5 d 4 b 4 s 3 v 3 c 2
Bigram Count ho 3 zn 3 pl 3 po 3 no 3 or 3 pt 3 go 2 qp 2 pr 2 gn 2 ry 2 hp 2 zi 2 ez 2 tk 2 ok 2 kp 2 fe 2 ut 2 tw 2 kq 2 eu 2 to 2 fr 2 eh 2
Trigram Count ezi 2 tor 2 kpt 2 hpl 2 ptw 2