No. 1 - Desert Treasure
I cannot think of a more iconic quest in OSRS – or in any MMORPG, for that matter.
When you got membership back in the day, this was the quest you had circled. This was the quest you dreamed of doing, the quest you built your character around being able to do one day.
Collecting the four diamonds of Azzanadra by defeating four challenging enemies – one representing smoke, one ice, one shadow, and one blood – in four very different settings, and then maneuvering your way through the booby-trapped Ancient Pyramid, grants access to the Ancient Magicks spellbook, which revolutionized both PvM and PvP combat nearly two decades ago.
This was the fifth Master quest to be released (the fourth was Roving Elves, the sequel to the aforementioned Regicide which is also ironically now an Experienced quest), and it was head and shoulders above Legends' Quest and Monkey Madness in terms of its overall difficulty.
Did you struggle most against Fareed, Dessous, Kamil, or Damis?
This legendary adventure also paved the way for the much more difficult Desert Treasure II, the new “hardest quest in the game” which was released during the summer of 2023.
This Grandmaster quest, which many believe it the single greatest quest in the game, grants access to four replayable boss fights after the quest against four more very unique enemies that present their own challenges and require extensive strategizing and planning to take down.