If both these buffs are present Ghost takes precedence.
Currently, if both are present and a character's HP reaches 0, it is "ghosted" and has the standard 3 turns left. Perfect Immortality is removed, meaning nothing - no effect.. nothing.
This seems wrong.
Perfect Immortality should revive the character and Ghost should be removed. The entire point of Perfect Immortality is to revive upon death. If a character is revivable, being "ghosted" is a negative, not a positive.