Complex sentence: Generally, they should be drowned, but the law code allowed for, in particularly severe cases, that the old punishment could be implemented: that is, the woman would be buried alive, and then a stake would be driven through her heart.
Split into simpler sentences: Generally, they should be drowned, but the law code allowed for, in particularly severe cases, that the old punishment could be implemented. That is, the woman would be buried alive, and then a stake would be driven through her heart.