In Ibn Fadlan's account of his time amongst the Rus on the banks of the Volga River in 922AD, he witnesses the sacrifice of a young slave girl by a terrifying figure known as 'the Angel of Death'.
Described as an old crone who is 'thick-set and sinister', she sounds very much like the archetypal witch/evil old hag figure of western mythology.
Are there any other sources that mention 'the Angel of Death' or female shamans/witches in Germanic societies of this era? As far as I understand it, Fadlan is generally deemed a reliable source, do historians trust this part of his account? Does the archetypal figure of the witch in western popular culture date from this era, or does the concept predate this?
The title "angel of death" is not a title that one can say is found throughout the whole old norse burial ceremonial culture. The description of the title on the other hand is more common. Meaning that the burial ceremonies was indeed conducted mostly by a woman and in a similar way that ibn Fadlan describes. But first we have to analyze the facts and findings that we actually have before coming to this conclusion.
If we go back to the ibn Fadlan account, the norse tribe that he encountered went by the name Rus. He encountered them while on his way to volga-bulgarian territory (todays Tatarstan, Russia). We can assume that he encountered them in the east Ukraine, south Russia, north Caucasus area, since he was traveling from Baghdad. Rus, at that time was a viking "tribe", people, from what is today called Roslagen, south east coast of Sweden and from the Finnish southern west coast. If we look on the historical facts and draw logical conclusions from it then we can all agree that it is highly possible that ibn Fadlan actually met this norse tribe, since we know that the first Slavic kingdoms, Kievrus and Novgorod, was indeed founded by a norse tribe that called themselves Rus. Kievrus and Novgorod just happen to be "on the way" and "in the same neighborhood" as where mr. Fadlan encountered these people. So by knowing this then we can also assume that the burial ceremony is something that originated from the areas where the Rus had either settled or came from.
Then if we leave the ibn Fadlan account for a moment and look at different norse burial sites around Scandinavia. What we can see then is that it is very different from place to place. Some are not cremated and some are. Some chieftains are not buried inside a boat and some are. Some have large stones over their graves and some don't. We see that the burials have some local differences and sometimes they are the same. I mean, in one settlement, or one area you can have many different types of burials and some of them show up in other areas and settlements, over different times as well. The one thing that is consistent is the mythology aspect and the items which shall follow the owner to the afterlife. And I shall also add that the "viking" burials, tombs, and stones are not only found from the time period 700-1100 AD. Many graves of this kind is dated back as far as 1700-1500 BC, which is the bronze age. Well before the viking age.
So now, let's jump back to the main question. Women in norse society had it a lot better than other women in European societies during that time. But compared to the standards of today they sure where not "free" in that sense. And this is also a very local thing that is different from tribe to tribe. Women was often connected to magic. If a woman was suspected of performing magic for dark purposes she would be killed, like in the later christian witch hysteria. But if she did magic for good, then she would be revered and praised. This is something that have been found from viking law documents. But still, one can't say that this represents the whole norse culture at the time, since there are so many local differences. BUT we can still assume that it was actually so. Why? Well there are one account of a large religious site that was in Uppsala, Sweden. Unfortunately it has not been verified by any archeological findings, only by one account made by Adam of Bremen. Many other religious buildings have been discovered by archeologists through out Scandinavia. Anyway, if we take all the temples, the Adam of Bremen account, all the common mythological symbolism throughout the region, the burial sites, the mythology itself one can find strong evidence of a large religious "organization" or a main common culture if you like, despite the small local differences. And since we can see this one can assume that maybe the angel of death was indeed a title that spanned the whole main part of that culture, even though there is only one account that mentions it. However, there are several accounts of Völva and Sejd. Völva is basically a norse woman who is a shaman that has magical powers and are in tuned with nature and can communicate with the gods. The same goes with a Sejd. Except that a Sejd was traveling from place to place and did more minor things like fortune telling and weather forecast. Even though sejd was considered a feminine art the master sejder was odin and there has been accounts of male sejders. And Sejd, sejds, sejding has many similarities to the Sami art Nåjder. The Völva was a more stationary and permanent force in the community and are more connected, mythologically, to the Norns. Maybe, during funerals, the Völva or the Sejd took on this title for mythological symbolism or maybe there was a separate designated person for this. We don't know. But one thing is for sure, "witches", women with superpowers basically, was indeed a common thing in norse culture and society.
EDIT
Here follows some more detailed info, from the danish national museum, around the subject. As requested.
Should also mention that in that link they explain völva, as mentioned above, as a person that perform sejd, "seid", in Danish. And sejd is also what the kind of magic/spells, or you can call it art is called. And they don't mention that a sejd, "sejdare", can be a completely different person with a completely different role. There are evidence that suggest that booth are correct. It is a matter of local practices mixed with language differences as well.
This is also a great page with alot of information regarding old norse culture.
https://vikingsociety.wikispaces.com/Death+and+Funeral+Rites
And here are tons of translated publications about norse studies and sagas.
In its original form, Ibn Fadlan's term for the old woman is "al-'ajūz," meaning just that. The term for the angel of death is "ma'lak al-maut," the actual Koranic name for Azrael (<Arazil) (32:11; 50:22), the angel or entity in charge of separating the soul from the body upon death. Mind that our traveler is interpreting what he sees in a language and terms familiar to him and/or his intended audience; not necessarily implying that the Rus' woman was actually a witch or indulged in dark arts.