Complex sentence: Grimble then sacrifices himself to allow the owls to fly away seeking the'Great Tree of Ga'Hoole'to warn the mythical Guardians about the Pure Ones' plan against them.
Split into simpler sentences: Grimble then sacrifices himself to allow the owls to fly away seeking the'Great Tree of Ga'Hoole. 'To warn the mythical Guardians about the Pure Ones' plan against them.