It was Taurun, one of Caiatl's advisors, that alerted her to the spectacle.
"In the square," she said, her deep voice laced with concern. "I've never seen anything like it."
Caiatl went immediately.
In the central square of Torobatl's weaponsmith district, a bright green flame licked the air. Umun'arath stood against the blaze, naked but for a waist wrap, in the custody of two guards. Her hide was carved with strange, crude symbols. When she saw Caiatl arrive, she threw her head back and laughed.
"Here comes the Princess-Imperial," she said. "To kneel before our new god."[I am Savathûn, whispering.]
Caiatl strode forward. "Let her go," she told the guards. Reluctant, they did as she asked. "What god, Umun? What heresies have you invented now?"
Umun grinned. "The god of war," she said, and the earth trembled beneath them.
[But the god of war has planted her armies elsewhere; it is her sister, smiling, that has taken the ear of the warchild Umun'arath.]
Caiatl stood before Umun in the flickering green light of the fire. "Your obsession is a weakness," she said. "And a threat to our prosperity."
"You can't stop it now," Umun lilted, breathless with delight.
[Xivu Arath, hear me.]
Caiatl didn't break her stare. "I have no choice but to—"
Umun, chuckling, raised her hands. They glowed. The fire behind her burned higher and chattered like rattling bones. "The war is all there is," she said.
As the chattering reached a fevered pitch, Caiatl made a decision. With the lightning-quick reflexes Umun had taught her, she unsheathed the ceremonial sword at her side and ran it through Umun's middle.
[You are war, and I conjure you with war and blood.]
She laughed and laughed and laughed until her mouth began to ooze. Until Caiatl, disgusted, pushed her off the sword with her foot. The body tumbled back onto the green blaze.
[A gift for my favorite sister.]
As the fire consumed the corpse, a gargantuan portal opened in the sky.