Hello Fenris (Thor must've been quite angry at your namesake
)
Interesting what you say about your last rites, I didn't know such traditions were still alive, and I'm glad they are. For us (Romanian Orthodox) we hold that one mus not die without having a lit candle in hand or close by...to light the way for the soul perhaps, but it's seen as an unfortunate thing if one dies without a candle.
About your sword obtaining a ritual significance, I have a small anecdote first recounted by a researcher oh some human psychology...when making meatloaf for the family, she had the constant practice of cutting the ends of the piece of meat when she put it in the oven; her mother had done it and so had her grandmother...why? There was no reason to do it, but the family felt that the roast was somehow better if she did cut the ends off. After some research, she uncovered that her great-great grandmother had started cutting the ends of the roast because it didn't fit in the pan! The anecdote is to illustrate that original cause or intent may be lost with each subsequent generation. The Aztec priest may have used a knife simply because it was useful, but each new generation of priest may have have had a new perception of it stemming from lack of understanding or from desire for something greater.
Regards,
Emanuel