Caesuras are often used by writers to create tension or suspense, and to control speed and rhythm. They break an episode into small chunks for the reader to digest, while also making it easier for the eye to jump from clause to clause, second by second. They create moments in a play-by-play. The effect, in this case, is to build momentum.

Notice how the phrases become shorter: the first clause comprises four words, the second eight, then three, two, and finally three short words, ending on the verb to kill. As film directors cut quickly from one close-up to another, so a writer can use punctuation to jump from one micro-event to another.

There is also a zooming effect. The first clause is like a wide shot view; it sets the scene. Following this, each phrase adds substance to the mental image.

Adding to this is the split prepositional phrase, from and to. The second clause begins, "from the foot," signaling the "to kill" which is to come. But it does not come immediately. Instead, the intermediary clauses draw in the reader, increasing suspense, like the steady tug of a bowstring, until the reader is delivered the conclusive preposition: to kill.

The Anglo-Saxon poem Beowulf is written with pauses, called caesuras, as well as other literary devices, to help the storyteller do a better job. The line you cite is a great example of caesuras, generally marked in the modern translations as commas, used to enhance meaning. 

Out from the marsh, from the foot of misty hills and bogs, bearing God's hatred, Grendel came, hoping to kill.

The pauses (commas, caesuras) in this passage are positioned to help the readers (listeners, in the original text) envision the stealthy movement of the marauding monster, Grendel. The narrator (singer/scop in the original) is able to build suspense by giving us the journey bit by bot and allowing us to envision what happens between the "bits."

If these lines were written in an informal prose form, it might sound something like this if the commas were given action and description: Out of the marsh (slowly and deliberately) from the foot of the misty hills and bogs (the place from which all evil things originate), Grendel came (sneaking his way into the town) hoping to kill. 

A lot of information is stored in those commas (caesuras), though it is implicit rather than explicit. In other words, the listener or reader kind of gets to decide what he envisions when the storyteller pauses. Each time there is a pause, the danger and the suspense intensify; and we know that a monster on the move bodes well for no one.