So, what is a "spoiler"?
The Encyclopedia Galactica contains a wealth of information taken from Asimov's novels of the Foundation universe. Visitors who may not have read all of these novels may come across information that they were previously unaware of which would ultimately spoil the enjoyment of the novel from which the item was taken from.
It is not the Enyclopedia's intention to detract from the excellent novels. Therefore, as a friendly warning, all vistors are respectfully warned that viewing may spoil your enjoyment of any unread novels.