-Murder Chest allows you to choose an ally type when it's benched.
-When your opponent plays an ally of that type, it's automatically destroyed.
This lets you choose what you want to destroy with much more precision than either Booby Trap or Death Pit, but if you don't know what's in your opponent's deck it might do nothing at all! Being able to target something specific is usually better than hoping you hit the right card, even if it doesn't allow you to pick a single card to destroy. Against an opponent playing a ramp yellow/red deck you might fear allies like Dragon of Fury. If so, just choose "Dragon" as the creature type. This way, you can kill that pesky dragon before it attacks you!
Strong against: a deck with a specific ally that you fear.
Weak against: quantity over quality decks, or a deck you are unfamiliar with.