Complex sentence: Jadis is responsible for the eradication of all life in Charn, but blamed the destruction on her sister; claiming she had offered to spare her sister's life if she surrendered, so the resulting destruction was the nameless sister's fault.
Split into simpler sentences: Jadis is responsible for the eradication of all life on Charn, but blamed the destruction on her sister. Jadis claimed she had offered to spare her sister's life if she surrendered, so the resulting destruction was the nameless sister's fault.