Unannounced phenomena are various events in Old School RuneScape that have at one time or another hinted to future updates.
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 What the... What was that? However, if the player was anywhere else, the chatbox message would instead be "You hear a faint rumbling from the far west..."
This in fact was a teaser for the quest, A Kingdom Divided.