Rhadamanthus will appear in the RPNo, not the GM's Author Avatar, but the mythological judge of the dead. TDS's depiction of the afterlife seems to be heavily inspired by Classical Greek Mythology, and we've already seen mythological figures such as Charon and Askalaphos, so it's entirely possible, if not downright likely. Maybe Rhad will be one of The Seven Masters.
Kylie will reveal...
Forest will not go to Heaven after the TrialsInstead, he will be recruited by Death Himself and become a new Death. He already has the scythe, the supernatural powers, and the work ethic. My guess is that certain people are chosen to become Deaths upon entering the afterlife, at which point the trials are used as a Secret Test of Character to see if they're right for the job.