In their black cocoons, the devouring force field was tearing away at their bodies with a power of 9(Cultivation Rank) × 9(Mind) × 8(Fenrir), which is 648 units of divine power.
This level of power is very weak and pitiful for a divine being. But compared to the power of a mortal, it is overwhelming. After all, one unit of divine power is easily 1,000,000 units of power for mortals. So, even though he can't use the power of his Cave Heaven right now, he can still crush a mortal easily.
In comparison, the best power that Forced Exchange and Money Speed can summon is 6(Cultivation Rank) × 6(Stat) × 6(Divine Metac), which is 216 units of divine power. This is why he can subdue the two of them so easily.
Clearly, he had been pretending to be weak when he allowed Money Speed to tackle him to the ground. He had done that so that Forced Exchange wouldn't be scared away. Once Forced Exchange got close enough, he unleashed the power of the Devouring Ability on them.
