Complex sentence: After Set was destroyed, Thunderstrike was possessed by the axe's murderous curse; as no-one was able to stop his rampage, Masterson chose to sacrifice himself in order to destroy the Bloodaxe forever.
Split into simpler sentences: After Set was destroyed, Thunderstrike was possessed by the axe's murderous curse. As no-one was able to stop his rampage, Masterson chose to sacrifice himself in order to destroy the Bloodaxe forever.