Which Quests, Places, Bosses etc. were previously a mystery, but now are discovered by Players?

Question

Few days ago a 7 year old secret of Dark Grounds was discovered. I was wondering which Quests, Places, Bosses etc. were previously a mystery, but now are discovered by Players?

Secret of the Dark Grounds discovered! – Tibia Secrets

Answer 1

Kissing a pig quest solved a mystery of years and years because no one knew how to pass the magical grass on femor hills

Mysterious ornate chest is a quest that started 12 years ago and lots of parts of it was discoverd but it is still incomplete and has a lot to be found about this quest and its bosses