Complex sentence: He sent them to put a spell on any man that they seen would fall in love and abide by their every command, which was to mine for a unknown metal which had the power to conduct lighting.
Split into simpler sentences: He sent them to put a spell on any man, that would fall in love so that he may be made to abide by their every command. The cursed ones mined for the unknown metal which had the power to conduct lighting.