Use the humans' greed against them

The remaining people looked at the crater in front of them, then at the bodies and blood scattered around. When they looked at Alexander again, their eyes held nothing but endless fear. 

The subterranean creature they had summoned at great cost couldn't withstand even a single punch from Alexander... this said it all. They had no means to fight against Alexander.

One of the elders was the first to mentally collapse, his body going limp as he fell to the ground, convulsing. Seeing the elder in such a state, the younger members behind him couldn't hold back their fear and knelt down.

"Who sent you here?" Alexander asked.

"It was, it was..." one of the men tried to speak, but after uttering just one word, he clutched his throat in agony. A wisp of black smoke rose from his neck, his veins bulging grotesquely.

"Spurt!" Then, a muffled sound came from within the man, and blood sprayed from his eyes, ears, and mouth. He fell to the ground, lifeless.