Evolution

As the dust mites finished killing Kyle, Shi Tian watched each and every single one of the dust mites undergoing an evolution. 

Their sizes began to increase and their legs started to grow some razor nails, coated in a liquid substance.

Despite their size having grown, it was clear that they are still considered invisible to the naked eye. After all, they are extremely microscopic beings, capable of walking through a human's skin without them noticing a thing.

'These dust mites are truly abnormal and amazing.' Shi Tian thought to himself. Although he didn't know why he could see them, he was clearly not going to question something this good. 

Kyle's corpse soon disappeared, including the skeleton, given that these dust mites' evolution was able to devour it entirely. That was the fearsome mutation in which even dust mites could cause such damage.