An Unnatural Dead-End is one that is formed as the Dungeon is being Explored, but that does not involve a regular Dead-End Tunnel Die. There are many patterns that could form an Unnatural Dead-End.

SACRIFICING GEMS

Unnatural Dead-Ends allow the Group to willingly ReRoll any of their Gems

Also, for each Gem ReRolled, a Trap will be activated!

About Regular Dead-Ends