Version 0 Edit
As seen above the page, the red warning box
Version 1 Edit
This is a spoiler done through a collabsable Table, but you need to edit Wikicode in the source view, which is not for everyone.
Version 2 Edit
Mouseover - again by using the source editor to add html span code
Show me more Spoils!
Version 3 Edit
And this, too, needs to be edited in the source, it simply adds same color to text and bg, thus making the text hidden but leaves a viewable placeholder
Here comes the spoil: No more Mystix for you! ... and you missed it!