Quick reply tp post # 40, clearly

The stranger has found a possessed weapon. He originally grabbed it with his left hand and tried to resist its will, he lost and was punished for hi imputance (the whole scorched, broken body thing). The sword led him back to the land of his, his father's, his mother's, etc. birth. To what end is unclear, maybe just destruction. Questions the PCs may follow up on : who is this guy, where did he get teh sword, why did he come here. Maybe the PCs can defeat the strnager, maybe the possession burns his soul and body out, maybe he recovers and gives a warning before he dies "Help me, I can't let it go." or words to that effect.
To tie in with a medieval setting/low magic, such a powerful weapon is feared. Maybe the PCs are considered tainted by the encounter and encouraged to find out what is going on. Maybe in his dying breath the stranger, if asked the appropriate question, mentions an abandoned hoard of treasure where he fouond the sword; often enogh motivation for many.
On having both "low" magic" yet PCs using magic I can share my own solutions. Decrease the frequency of spell casters, only 1 in 1000 to 1 in 2000 have the intelelct and determination to make it through the training alive and sane. If population is low most villages will not have a spell caster and even temples/churches will be served by lay brothers and sisters. If you are seeking to have a medieval setting with "The Church" this gives some interesting possibilities. Now 1 in 2000 may seem like a low number, it is in many ways, but I beleive this is about the per capita of doctors in the US. So people will know of magic but might go their whole lives without seeing a spell cast, especially if they live in the countryside.
To minimize effects on society, cut out permanent effect spells as much as possible and make magic item creation, besides say scrolls and/or potions, very hard, exspensive and time consuming. The only reason they are not incredibly rare is they last a long time, so a stock has built up over the millenia. Of course many are lost in "dungeons" or what have, places where PC tend to go.
On attitudes to magic. Maybe religion dislikes mages, they both compete for the same limited pool of potential apprentices. Rulers, being what they are, will use what magic they can get, of course they might encourage the common folk to fear and distrust spell casters. They may not want a witch burning mentality, after all they still want spell casters. However, if they people dislike spell casters it makes it that much politically harder for them to ursurp the power of the King.
If any of these magic ideas seem promising I can go on, I've worked for a long time trying to work out the proper mix ( I too want PCs slinging magic but don't want magic ending up as everyday technology) and can go on more when I have more time.