Complex sentence: When Moonstone was held prisoner by the Masters of Evil, Ogre slipped a key into her room which released her from her shackles, this helped Moonstone and the Thunderbolts defeat the Masters.
Split into simpler sentences: When Moonstone was held prisoner by the Masters of Evil, Ogre slipped a key into her room which released her from her shackles. This helped Moonstone and the Thunderbolts defeat the Masters.