Vault Inscription

A powerful spell seems to shroud the deepest portions of the Pits of Frengra, and it seems to originate from a singular Vault-like door. The door bears an inscription, which despite two decades of study has only been partially translated.   The translated segments of the inscription are as follows:   FIRST THINK OF THE PERSON WHO LIVES IN DISGUISE WHO DEALS IN SECRETS AND TELLS NAUGHT BUT LIES NEXT TELL ME WHATS ALWAYS THE LAST THING TO MEND THE MIDDLE OF MIDDLE AND END OF THE END AND FINALLY GIVE ME THE SOUND OFTEN HEARD DURING THE SEARCH FOR A HARD TO FIND WORD NOW STRING THEM TOGETHER AND ANSWER ME THIS WHICH CREATURE WOULD YOU BE UNWILLING TO KISS AU BKMJ XPZ BSL ZPDH GFET IQH KZXA SLISHM BSL UPV UIRV IPHR JABXOC KSE IOP KZT MBIJ TTNRVV QDC SVFUTMG