Another day passed. Jack was still inside the forcefield cell. What he had been doing was trying to mask his mana with the mana controlling the forcefield cage. He was doing the same thing he had done to the Chalice of Blood every night. He was trying to fool the mana from the rune diagram into accepting his mana as a part of itself.
If he was able to insert enough of his camouflaged mana, he could exert control over the forcefield, just like how he created the small slit a day earlier. To open a hole large enough for him to escape, he would need to gain greater control.
In the first few hours of his captivity, he had tried brute force. He might not be able to use skills, spells, or tools, but he could still move and manipulate mana. He had tried using all his sword arts to break the wall. Most failed. Only the Nine Yin Phantom Sword was able to penetrate the forcefield wall, but the hole it created was too small. That hole also quickly closed afterward.