The envelope doesn't seem to be at all magical, apart from a cursory magical signature in the wax seal as proof of authenticity. There are ways of concealing prana bound into an object, but as far as Laoise can tell none of them were used here.
Inside the envelope is an embossed invitation, stamped with far too much gold foil, which reads:
All Masters and Servants of the Fifth Holy Grail War are hereby invited to a banquet in an evening's time as a temporary reprieve, courtesy of Florianus von Einzbern, Master of Berserker.
The location will be provided upon acceptance of the invitation and subsequent R.S.V.P., to forestall any attempted treachery on the part of either Master or Servant. Be forewarned that on the night of the banquet, all guests are under the protection of the Einzberns, and any attack made either at the banquet proper or while guests are arriving or departing will be considered an attack on the Einzberns as a whole, and no penalties will be levied against guests who retaliate in kind, lethally or otherwise.
Should you plan to attend, deliver your response to the Church official overseeing the War, Kotomine Kirei, by tonight at midnight, either in person or by familiar. Guests are strongly encouraged to wear formal attire.
Cordially yours,
Florianus von Einzbern, Magus and Master of Berserker.
The note doesn't at all match with what Laoise knows of the way Florianus talks, but the seal seems entirely genuine.
