First referenced:
The Desolate Guardians (Part 3)
Other references:
'I think I may have somehow missed the end of the world... (Part 3)'
Purple slice is a section of a fractured reality, characterized by a dark purple section, or slice, of sky. The Purple Slice (or 'crazy' as it was alternately called by Jonathan Cortin) appears to cause people observing it to go temporarily insane, and attempt to claw their own eyes out or cause other forms of self harm. The prescribed method for dealing with purple slice is to tie yourself up sufficiently well to prevent self harm, but loosely enough to escape subsequently to avoid other dangers.
Purple slice should not be confused with the jagged, glowing purple rift in space and time caused by The Crushing Fist. These rifts instead lead to The Raving In-betweens, an area that exists between the normal space-time of the various universes in the multiverse.
Heath communicated these instructions to survivors, who accidentally misinterpreted them as tying the rift up. This proved to be futile as expansion of the rift promptly tore through the rope and continued to expand.