Okay, so my first ever pathfinder campaign included a recurring NPC that the party somehow kept having to save from outrageous situations. He was ostensibly a traveling merchant who had a talent for creating rare and wondrous weapons and armor from the remains of whatever the party had saved him from, when in reality he was a Rakshasa Maharaja who was planting Raktavarnas (degenerate rakshasa relegated to the forms of objects) on the party.
When his identity was revealed at the very end, the party had the double shock of having their greatest benefactor turn into the BBEG AND having their relics and magic weapons literally sprout legs and join the enemy in fighting against them. ^_^