What is the end of law is "both good and evil"?

Hebrews 5 begins a three chapter focus on the priesthood, and order thereof Jesus Christ, being "after" the order of Melchisedec, which is mentioned no less than six times in Heb 5-7, twice in Heb 5 (perhaps to make a point); And as if comparing the two orders of such priesthoods as an allegorical before/after scenario of law/grace. It also allegorically notes Christ is only the "author" of author/finisher of "eternal" salvation; As if the head of the body decides what's best for the whole body is no law, since the result of priests adding law to grace results in infirmities and a dead end (Heb 7:23). The conclusion of Chp 5 states "ye" folk, such as the Hebrews (plural), are as an adult "babe", unweaned from law, and unable to discern both good + evil (grace + law) ends bad.