Unannounced phenomena are various events in Old School RuneScape that have at one time or another hinted to future updates.
Will o' the wisps[edit | edit source]
On the 29th of June 2004, prior to the introduction of fairy rings, will o' the wisps appeared at various points around RuneScape in all of the locations that the fairy rings would be placed.
Ground shaking[edit | edit source]
On the 29th of December 2016, prior to the release of Chambers of Xeric, a chatbox message stated "You feel a disturbance deep below the ground, as if some ancient beast had stirred." with the ground shaking at the same time.
Ground rumbling[edit | edit source]
On the 19th May 2021, around 17:42 UTC, if the player was located at the continent of Zeah, a chatbox message stated "The ground beneath you violently shakes." with the player character exclaiming However, if the player was anywhere else, the chatbox message would instead be "You hear a faint rumbling from the far west..."