Based on this excerpt, it is reasonable to conclude that neither twin could die because they were immortal gods. The excerpt tells us that none of brothers died, and also it points out that they are the creators that once stepped on separate paths. They are still alive, but not in the sense that we are used to think. Each one has its duty and now they both look at the world from different sides.
C. It killed nearly 80% of the population
I believe that the answer is C, or It is correct because it indicates that Callie is not friendly today.
I believe there is only one comma in between limping and exhausted