I'm just sort of confused on the whole Calliope thing... how did she come back to life after Caliborn killed her? Didn't they share a body? What happened to the other Calliope in her God Tier that won?

Calliope came back with the aid of the Ring of Life which can bring a ghost that wears it back to life. The Cali twins did share a body but after Caliborn had Calliope killed Caliborn took control of their main body and Calliope lived as the ghost of her dreamself.  Alt-Calliope was at the epicenter of the Black Hole so she was almost definitely sucked in to it