Probably the best spell was one of the very first ones in 1795, because they actually showed her gathering herbs, and she needed to get someone to steal an article of clothing for the link to make it work.
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I really liked the spell she put on Laura Collins at the end of Laura's story in 1897 (just watched that one recently).  Another 1897 spell that's really cool is one she performs with the aid of a "jewel of antiquity"--it looks like something from Ohrbach's costume jewellry department, but I love it anyway.

Do you want episode numbers or DVD set information for these?  Or are you just generally curious?

Yes, if you could tell me which DVD set these are on, that would be great.  Also the one that PennyDreadful mentioned would be interesting to know.  I was able to find the others thru some searching.

What in your opinion are the most interesting episodes dealing with witchcraft in the series?

Hi  I've heard a lot of interesting things about Dark Shadows and want to check it out. Since theres like a zillion episodes, can someone make some recommendations
on what are the best / most interesting  episodes or eras to check out?  thanks