Mortulaca

To add to the difficulty of the nether, a thorny ground cover would prove interesting.  It would spread across the ground and make movement more restricted as a player would have to remove this surface in order to walk safely around. Fleeing a ghast or other hostel mob, would require the player to avoid this obstacle as well.  It would do damage to walk across and cause disruption to walking, moving the player slightly as they take damage.  It would be the thickness of carpet and would spread across stone, sand, netherrack, soul sand, and gravel, etc. It could be covered in a few small flowers (red\purple) to make it look distinct. It should not be able to be lit on fire, so it would not be easily destroyed by the many lava flows and flames.