Clench Your Teeth, Cerberus!

Achilles' arms groaned, healing and shattering in succession under the Styx's water influence. If not for their goal, he would have taken his time to maul down the beast. But this strategy was also fine—pain was his oldest friend. "Adam, now!"

The second his words left his mouth, the flames swirled. Like dancing tendrils, they passed him by, disappearing into Adam's crevices as he squatted on the beast's lips and gripped the closing fangs.

The pressure crushing him weakened, and the suffocating heat vanished. Seizing the opportunity, he hurled his round shield upward.

BAM

As if stamped, the intricate engravings carved themselves onto Cerberus' flesh. The tremor travelled through its skull, shattering its snout with a terrifying crunch. Blood poured from its nostrils in two scarlet jets before its eyes wobbled and lost focus. 

The momentary daze further weakened its bite. But its right head, still intact, snapped to devour Adam.