Catholics believe that when the communion host is consecrated by a priest it actually becomes the Body of Our Lord, Body, Blood, Soul and Divinity. It remains such as long as the accidents remain. That is why this is horrific to Catholics. Satanists will actually steal consecrated hosts for the purpose of desecrating the body of Our Lord.
It is horrific to Protestants too. Of course, the person who will suffer the most horrible consequences is the desecrator himself, who by consuming without belief "eats...damnation unto himself".
God is not mocked.