Complex sentence: Nerissa comes into the court and when Gregor mentions the Bane is the baby, she says that the baby was not Boots but was the Bane.The bane is important to the rats just like Boots is important to Gregor.
Split into simpler sentences: Nerissa comes into the court and when Gregor mentions the Bane is the baby, she says that the baby was not Boots but was the Bane. The Bane is important to the rats just like Boots is important to Gregor.