Divine mana and demonic mana, conflicting forces, now coursed through Allen's body, a peculiar and dangerous coexistence that defied all logical explanation.
Based on Petronella's speculation, Allen's body had anomalies due to living raised in a dungeon, which was also impossible. Humans who live in a dungeon would not be able to withstand demonic mana, and many other factors make that impossible, even if he lived in the "safe territory" in the dungeon. The concentration of the place, the air pressure, and many more factors make the baby wouldn't survive living there.
But Allen survive.
Petronella's speculations stop at the "Other-worlder" concept, which is still mysterious. The other-worlder's body adept at absorbing mana, must have also absorbed the demonic mana inside the dungeon, and then supported by a (probably) Nortish body that has a large mana capacity and control, making Allen adaptable in the dungeon.