(Some notes on a previous installment.)

> Fjörsváfni

The second element could be related to `svefn' "sleep". Just my
guess, but maybe the idea is that it puts life to sleep, i.e. kills
people. Magnus Magnusson and Hermann Pálsson translate it Life-Taker,
as Gael noted.

> Sagt hefir þú oss þá sögu er oss mun eigi setugrið bjóða

`setugrið', n.pl. can mean "abode", or – as here – "rest". So:
"You've told us a tale that promises us no rest." That is, the news
you've given us bodes ill for our chances of a quiet life. What
you've told us means that we probably won't be left in peace.

> Þá mælti Glúmur: "Hvort (hvárt) mun Skarphéðinn nú dauður?"
> Then Glúm spoke: Why, will Skarphéðin now (be) dead?'

`hvort' / `hvárt' just introduces a yes-no question: "Will Sk. be dead
now?" or "Is Sk. likely to be dead now."

> og eru slíkt heimskir menn sem þú ert

I don't think we necessarily have to consider it an adverb. Compare
the use of neuter singular in `margt manna' "many men", `hvat manna
ert þú' "what (manner of) man are you?" (who are you?).

> (ván, often when you see `o' in Modern Icelandic spelling, look

under `á' in Zoega)

Specifically, following a `v'.

> Mun sá allur einn er nú á dvalar og hinn er þá mun verða svo hræddur

að eigi mun vita hvert hlaupa skal

I wasn't sure about the syntax of this. I wonder whether `dvalar' is
acc.pl. of the noun `dvöl', and `á' the 3rd person present sg. of
`eiga' [ http://lexicon.ff.cuni.cz/png/oi_cleasbyvigfusson/b0110.png
]. Compare: `kvazt þar skamma dvöl myndu eiga'; `Ásgrímur kveðst þar
mundu eiga skamma dvöl'. Konráð Gíslason and Eiríkur Jónsson
punctuate thus: `mun sá allr einn, er nú á dvalar, ok hinn, er þá mun
verða svá hræddr, at eigi mun vita hvert hlaupa skal.' The other
alternative is that `dvalar' is the 3rd person singular indicative of
the verb `dvala', and `á' an adverbial particle.

> og klofnaði hann allur í sundur

"it was cloven completely in twain" / "it split completely in two"
(the shield is the subject). The -na verbs are intransitive.