Complex sentence: The souls of dead ancestors are invoked by the Iban when seeking their blessings and showing respects for their souls usually during Gawai Antu (Festival for the Dead) and when visiting their graves.
Split into simpler sentences: The souls of dead ancestors are invoked by the Iban when seeking their blessings. They pay their respects to their souls during Gawai Antu (Festival of the Dead) and when visiting their graves.