The spread of Christianity didn't immediately dent paganism in Scandinavia. The territory was so vast, the cultural isolation of its far-flung regions so great and rate of Christianisation so slow that edicts from any centralised church were to some degree ineffective.

Despite various missionary attempts from various angles, only from the 11th Century did Christianity emerge as a significant force in Scandinavia. Part of the problem, perhaps, is that core to these conversion tales is often a magical duel between the magic of Odin and the magic of Christ. Christian sorcery - or miracles - inevitably win out, but stories of this sort suggest a sort of equivalence that the early Scandinavian church could have probably done without.

One man's prayer, after all, is another man's rune casting.

The uniquely Scandinavia nature of Christianity ensured that curses, spells and sagas maintain a grip on the population to one degree or another across the Medieval period until at least the 13th Century. It wasn't about paganism vs Christianity, either, but Scandinavian Christians who cherrypicked from belief systems to suit their needs.

Magic, after Christianity, was used as it was before Christianity in a variety of every day tasks to offer protection from illness, shelter from supernatural forces, assistance in childbirth, foresight about weather and harvests, recovery of list articles, and so on.

In Norse sources, magic is divided up into galdr and seiðr, with the former predominately male rune magic and the latter predominantly female ritual magic. Galdr is generally seen as more passive and benign, while seiðr is later depicted as evil - there's certainly accounts of seiðr magic being used to kill on command or bewitch men.

One vivid 13th Century account of seiðr depicts a wise woman being summoned for a specific task:

It was Þorbiörg’s practice of a winter to attend feasts, and those men in particular invited her to their homes who were curious to know their fate or the season’s prospects. Because Þorkell was the leading householder there it was thought to be his responsibility to find out when these hard times which had now troubled them would cease, so he invited her to his home, and a good reception was prepared for her, as was the custom when a woman of this kind should be received.

Þorbiörg (this is a good time to apologise for not using the proper Norse characters in Scandinavian words and names: sorry, everyone) is treated and depicted as a women apart, one worthy of great respect. She is fed animal hearts and her attire is commented on in great detail placing her firmly in the Shamanic tradition:

She was wearing a blue cloak with straps which was set with stones right down to them; she had glass beads about her neck, and on her head a black lambskin hood lined with white catskin. She had a staff in her hand, with a knob on it; it was ornamented with brass and set around with stones just below the know. Round her middle she wore a belt of touchwood, and on it was a big skin punch in which she kept those charms of her which she needed for her magic.

The magic isn't accomplished by her alone, and Þorbiörg draws upon the women present to chant - suggesting a familiarity with the practice, perhaps even with this specific rite:

The women now formed a circle round the platform on which Þorbiörg was seated. Gudridur recited the chant so beautifully and well that no one who was present could say he had heard a chant recited by a lovelier voice. There seeress thanked her for the chant, adding that many spirits had been drawn there now who thought it lovely to lend ear, the chant had been so admirably delivered - spirits “who before wished to keep their distance from us and give us not hearing. And now many things are apparent to me which earlier were hidden from me as from many others…” After this men approached the prophetess and inquired, each of them, about what they were most concerned to know. She was free with her information and little indeed of what she said failed to come about.

You can get a sense of just how widespread and varied the practice of magic was in legal documents such as the mid-12th Century Borgarþing laws from the Oslo fjord area. They are are so specific in their details of what exactly was prohibited, that it's not unreasonable to assume this was happening:

But if a woman bites off a finger or toe from her child and does that [in order to secure] long life, she is fined 3 marks. The worst witch is she who destroys a man or woman or child or cow or calf. And if sorcery is found in bedding or bolster, the hair of a man or nails or frog feet or other talismans which are thought wont in witchcraft, then a charge may be made […] That is a felony if one sets out and rouses trolls thereby. That is felony if one kills oneself. That is also a felony if one journeys to Finnmark for soothsaying.

Elsewhere in 12th Century Sweden, Västergötland to be exact, there's a small charm amulet with a runic inscription that reads:

[I] practice witchcraft against the spirit, against the walking, against the riding, against the running, against the sitting, against the sinking against the travelling, against the flying. Everything shall [lose] its vitality and die.

Ironically, as Christianity's influence strengthened - and the concept of 'Witchcraft' with it - the idea of charms, potions and countermagic gained a new significance.

Well into the Christian ascendancy, Christian interpretations of magic persist and a Danish leechbook from the 14th Century recommends inscribing a particular Latin blessing on the gateposts to protect animals from thieves and wolves, and the recitation of the 'Our Father' while the herbs blend in a potion to curb wanton behaviour.

Source: Witchcraft and Magic in the Nordic Middle Ages by Stephen A. Mitchell and Nordic Religions in the Viking Age by Thomas DuBois

EDIT: Changed some of the characters to make it Scandinavian-compliant!