Favorite is easily While Guthix Sleeps. This quest had great puzzles, combat, story. Really everything anyone could ever want from a quest.
Honorary mentions:
One Piercing Note: Probably the best standalone quest, this adventure features a story that is entirely on its own and actually beats out some of the lesser series.
The World Wakes: My favorite combat-centric quest. This is an awesome adventure that is completely integral to the upcoming story of the game, and the ending actually made me feel something for an MMO character. What is this, The Last of Us, making me care about characters?
Rune Memories: This makes the list for exceeding my expectations more than any other quest I have ever played. I went in expecting a shallow, low-level quest that could have potentially ruined the older lore of runecrafting and the wizard's tower. What I got was a deep look into the tower's history as well as a fun journey with the best of the Signature Heroes.
08-Aug-2013 23:15:06