The Spyder easter eggs were the most prominent easter eggs in Riven. Actually, there are several different easter eggs  (six known so far), all unlocked with the same rather complicated and time consuming procedure. Essentially, the player will need to click through a series of hotspots, spread both in time and space throughout the game. There are also certain hotspots that one must not click.
Clues to find the hotspots to click were released by Spyder. There was, however, no official word on how to trigger the actual eggs; only how to unlock them. The rest was up to fans to discover by themselves.
Where creatures float and waters rise,
only one of five will open.
The one that stands out is your prize,
small, orange and unbroken.
Slowly rising from the bed,
and closer to your goal.
Clear the cobwebs from your head,
and search the empty bowl.
Control the bridges, enjoy the view,
and think about the ride here.
Something you see just can't be true,
so make the mirage disappear.
It rises from the water,
and asks you to come in.
Don't yet go where it's hotter,
first find the sign of Gehn.
Call the first magcar again,
and search the rocks nearby.
The name of an historian
is just four pixels high.