The letter would read.
Greetings insert name of leader here. You are cordially invited to a coronation on Nap to take place one week from today. Therefore I hope you do decide to come after all as you might enjoy it. Don’t bring over 5 soldiers to protect yourself. Also any anti human genetic weapons we find on you will be confiscated. If they are found you have signed your own death warrant.
Signed
WH General Ator