Complex sentence: However, with Byakko's newly developed weapon named Crystal Jammer the Suzaku crystal that kept Milites at bay at Rubrum shatters, leaving the nation vulnerable to attack and is forced to surrender to the superior nation.
Split into simpler sentences: However, with Byakko's newly developed weapon named Crystal Jammer, the Suzaku crystal that kept Milites at bay at Rubrum is shattered, leaving the nation vulnerable to attack. Suzaku is forced to surrender to the superior nation.