This is a Royal Investigator Mission. Speak to Skaros in Castle Blackthorn and say “Investigation” to him to begin it. It will run for 7 days, and reports of what you discovered should be made at the report on the UOEM page for credit. In particular, report on what the Name of the secret is... you may have to think a little to work out the next steps of the chain! The first person to submit a report detailing the secret of the Ordo Solstitium will be credited in the announcement of said secret.