Complex sentence: He reigned until 1796 when Agha Muhammad Khan conquested Khorasan and had Shah Rukh tortured to death because he thought that he knew of Nadir's treasures.
Split into simpler sentences: He reigned until 1796 when Agha Muhammad Khan conquested Khorasan. He had Shahrokh tortured to death because he thought that he knew of Nadir's treasures.