Complex sentence: While they were ultimately successful in imprisoning their enemy, they would die from the injuries they sustained during the battle and the Goblin Entity managed to escape its prison several years later by attaching itself to the life force of Madelyne Pryor.
Split into simpler sentences: While they were ultimately successful in imprisoning their enemy, they would die from the injuries they sustained during the battle. The Goblin Entity escaped its prison several years later by attaching itself to the life force of Madelyne Pryor.