I LOVE THIS!!!

Despite Ren's body having incredible defensive properties, and his regenerative abilities that were nothing less but ridiculous, he is not immortal, he can be hurt and killed. Ren's defense can be penetrated and his regenerative abilities can be exhausted. 

The group of Demi-Gods were very much capable of breaking through Ren's defense and over-taxing his regeneration. Each strike of the Demi-Gods was strong enough to destroy a small planet, and their speed is something that constantly created sonic booms. 

The battle between Ren and the Demi-Gods was destroying everything in sight. If they weren't in the upper planes which have distances measured by light-years and were in the lower planes instead, they would have destroyed numerous planets already.