At that moment, everything—what he saw in the tapes, clues discovered at the scene, and the reality before him—flitted across the Mummy's mind. He was certain he had walked into a cunning trap.
His specialty lay in mental prowess. Against someone who hasn't been through qualitative changes—what they call an "Inhuman" in China—he would have an overwhelming advantage. Even if he took on a few of them at once, he was certain he could make quick work of them. However, his powers were much less effective against a Demigod, even if it wasn't a full-fledged one. He could win in the end, but not without a tough fight.
And if he was caught in a tough fight, he would be at a disadvantage in numbers. If Siris and his companions fought well, he could even be in grave danger. Moreover, covering a long distance to chase them down had taken a toll on his energy. Even if it was one-on-one, he wasn't certain if he could defeat the well-rested enemy!