The Benevolent Fairy powder... Part-1.

Walking down the narrow path in the cave, Jareth used the glowing mana orb to illuminate the path.

Right now, Jareth and Aria are at least ten kilometers deep underground; oxygen is nearly nonexistent in this place; and the temperature is also very hot.

But for individuals in grades 3 and above level individuals, lack of oxygen and fluctuations in temperature matter very little.

You can just deploy the mana barrier and use mana to forcefully pull oxygen molecules from the air inside the mana barrier.

Even if there is no oxygen outside, they can still manage to survive on mana alone for a day or two.

On the other hand, Grade 1 individuals don't even need oxygen in the first place; they can just use the mana as their primary source of energy in the body.