The Spectral Pickle Factory has appeared only 17 times in the history of the kingdom. It used to appear whenever it felt like it; as Mr Skullhead said, "None may know the hour of its coming and going." Currently, it makes an annual appearance every April Fools' Day. When it does appear, it can be found in The Nearby Plains.
A primary stat of 50 is suggested. If your main stat isn't high enough, you'll see the following message:
As you near the howling gates of the Spectral Pickle Factory, the hairs on the back of your neck stand up. Then the hairs on the neck of your back stand up, and it really freaks you out, since you didn't know your back had a neck. The point is this: you're too scared to go into this Factory.
(It is recommended that you have at least 50 <mainstat> to adventure here.)
Players who attempt to visit the Factory after it has disappeared will see the following message:
The Factory has faded back into the spectral mists, and eldritch vapors and such.
Pickle Factory Appearance II.5: April 1, 2005 (Starch 7, Year 9) (The Factory's image appeared in its normal spot, but there was no way of entering the Factory itself.)
Pickle Factory Appearance IV: April 1, 2006 (Jarlsuary 4, Year 13) (The Factory's image appeared in The Distant Woods, but it could only be entered through The Nearby Plains, where the Factory was located in its normal spot, but was invisible.)
Auto-attack is disabled against all monsters in this zone.
References
The Factory is possibly a reference to a photo of an abandoned pickle factory that appeared in the browser game, Quest for Schlitz, which was written by Jick and which is older than the Kingdom by a few years.