Also know as sword beads, life stones, healing stones etc and taking many forms such as glass beads, pieces of amber or similar they are objects that have been found in conjunction with swords in Anglo Saxon and Scandinavian burials. They could have been something to do with belt or scabbard fittings but its widely though that they were some sort of ritual item/ good luck charm. There's references to them, especially in Norse sagas, as being able to heal wounds caused by the sword. There's better descriptions on the net but that's my take.
for me they are a nice bit of bling to go on a couple of replica Anglo Saxon seaxs I have. Tillerman Beads do some really lovely copies of glass ones that have been excavated but I couldn't justify the expense.
ATB
Tom