Complex sentence: Plunder Island is the first island that Guybrush visits in The Curse of Monkey Island; when he arrives it is under siege from the evil zombie pirate LeChuck; though thanks to Guybrush his plans were foiled but the Fort was beyond repair.
Split into simpler sentences: Plunder Island is the first island that Guybrush visits in "The Curse of Monkey Island". Thanks to Guybrush, his plans were foiled but the Fort was beyond repair.