His breakthrough to the fourth circle was a success, but there were multiple obstacles in the process. He felt like the mana core in his chest would explode. The breakthrough had to put a massive amount of pressure on his crystalline mana to advance it into the next level and turn it into a gaseous state again.
The amount he needed to absorb for the whole process was downright horrendous. Thankfully, before the breakthrough, already expecting something like that he had made a direct connection of his engravement chamber to the mana well right beneath, otherwise he would have sucked dry almost all the mana in the tower itself as well the surroundings of the tower. Boundless strength coursed through his veins, and a greater qualitative change occurred this time.
