Definitions

palimpsest  pal-imp-sest   |   /ˈpælɪmpsɛst/

•  A manuscript or document that has been erased or scraped clean, for reuse of the paper, parchment, vellum, or other medium on which it was written.
• (archaic) Monumental brasses that have been reused by engraving of the blank back side.
• (astronomy) Circular features believed to be lunar craters that have been obliterated by later volcanic activity.
• (geology) Geological features thought to be related to features or effects below the surface.
• (computing) Memory that has been erased and re-written.
• (cultural studies) The partial erasure of or superimposition on an older society or culture by a newer one.
• Something bearing the traces of an earlier, erased form. 

puissant  puis-sant  |  /ˈpjuəsənt/, /ˈpwɪsənt/

• (archaic or literary) Powerful, mighty, having authority. 

posse  po-si |  /ˈpɒ.si/

• A group or company of people, originally especially one having hostile intent; a throng, a crowd. [from 17th c.]
• (now historical, in later use chiefly US) A group of people summoned to help law enforcement. [from 17th c.] 
• Coordinate term: vigilante
• (US) A search party.
• (US, Jamaican, slang) A criminal gang. [from 20th c.] 
• (colloquial) A group of (especially young) people seen as constituting a peer group or band of associates; a gang, a group of friends. 

References

• The Sinai Palimpsests
• Palimpsests in Geology
• The Age of Erasable Books
• The Preservation of Neglect
• The Archimedes Palimpsest
• A Review of Wolf Hall (puissant in para 4)
• California Allows Public to Refuse "Posse Comitatus"
• Margaret Thatcher quoting Milton (puissant)
• Game of Thrones (Wiki of Ice & Fire)

Sillyness

"possible podcast plot premise about the puissant probing of the papal posse possibly proving that the purloined parchment is a palimpsest plastered over a pointillist painting of problematic peacocks playing with porcine pigs"