The earth wolverine and the Qilin Julius had carefully cultivated merged. Both matured through the thousand-day method that had refined their capabilities beyond what time alone would achieve. Both at the same Gold 1 rank and balanced so perfectly their energies complemented instead of creating any friction.
He began the fusion but kept it contained in his human body rather than permitting the beasts to manifest physically.
It was a tactical necessity imposed by the tunnels' small space where they'd have to advance after each chamber. Walls that were indestructible for his power level by design of the ancient civilization that had created them.
The tunnel couldn't accommodate creatures of the size that the vast majority of Gold-rank beasts reached when fully manifested, let alone fused ones. It was a restriction that would have made using the power of their body appropriately impossible if he'd attempted invoking the second copy outside his own human body.
