[@Shadow Dragon] exactly and unless Kevin wants to be killed by Dionysus he can't kill them also the maenads are nymphs who are incredibly strong and durable 

The Maenads look like teenage girls. Their skin was webbed with bright capillaries, their eyes were severely bloodshot, and their lips were redder than normal.[1] When they get overly excited, their fingernails turn into long, white talons, and their teeth elongate into wolf-like fangs.[2] The Maenads wear tunic dresses of loose purple, red silk with leaves tangled in their hair, and tiny vipers adorning some of their heads. Some carried large twisted, wooden branches topped with a giant pine cone with some wrapped with living snakes.

Like I said if Murphy knows he can't beat someone normally who in this case is kevin Murphy will expend a lot of energy controlling the maenads to hear them it's his trump card