Possible Clues:

• Z, to a sorority pledge
• Greek consonant
• Greek letter that surprisingly isn't last
• Greek alphabet letter
• Unknown projected delivery date for letter from abroad
• Unknown insurgent worried Spartan character
• Greek letter that one might expect to come last
• Z, in Athens
• Letter that's only 25% of the way through the Greek alphabet, surprisingly
• Greek letter (but not the last one)