Maritzis's "Water" possessed healing traits and had reattached the severed arm to the wound.
The G virus was also aiding in the continuation of the arm, performing cellular level division and regeneration, coordinating the connection of nerves.
At the same time,
having his arm torn off alive,
this bone-deep pain significantly stimulated Han Dong's brain, causing his "fear emotions" to greatly recede.
Recalling how he had just pressed down on the monster's head, letting his companions escape without regard to himself, a terrifying thought suddenly emerged in Han Dong's mind.
"Dumps! Change the route, run along the safer areas first... I have an idea!"
"Hmm? At this point, what idea could you possibly have?"
The map derivation had been completed, and all members had voted to move to the lower level, while Han Dong himself had sacrificed an arm as the price for his teammates' complete escape.