The red ash is a key element in the gameplay of Infernium. It appears as lines in the floors in multiple levels of Infernium and you can use it at your own advantage. In short. Enemies of all kind won't be able to cross the red ash so you can use it to run away from them.
If you become unreachable when crossing the red ash (for example, entering inside a circe of red ash) the enemies will eventually stop chassing you (you will notice this because the sparks at their feet will deactivate). On the other hand, if you cross the red ash but you are still reachable, enemies will continue to chase you but they will take a diferent route to get to you; a route that doesn't get them through the red ash.
The red ash is really usefull to put some distance between you and some foes, specially the Dark Cloak. If used clearly you can put a big amount of distance between you and them.
Commonly found in the Wet Cave and the Waterfall Arena, it is currently possible to found red ash in almost all maps of Infernium, including the Heaven. Know the patterns of the red ash in the floor and you will be able to progress through the challenges more quickly.