The twin's facial expressions turned from maddened glee to fear really quickly under the new assault of Marshallo's refined aura.
Unlike before, when his aura had that wild attribute to it that made everyone kneel to him. Now his aura had the quality of a seasoned veteran coming back from war instead of a jungle's beast that could rip you to shreds for the smallest movements.
His death had catalyzed something in him that had been dormant since he had been chosen by one of the gods... after all, this was his first-ever death.
The twins realized they made a mistake after Marshallo got rid of the poison very easily, but those actions weakened him a little bit further as he lost quite a bit of blood.
His defenses weren't as strong as before due to his weakened body. And now, he was further weakened, making the half and half duo think that they had a chance against him, regardless of the improved quality of his aura.