Complex sentence: During their investigation, Artanis and Kerrigan learn of the Xel'Naga originate immensely powerful beings who originate from the Void and are responsible for the creation of life in each universe.
Split into simpler sentences: During their investigation, Artanis and Kerrigan learn of the Xel'Naga's origins. The Xel'Naga are powerful beings who originate from the Void and are responsible for the creation of life in each universe.