The core members of Umbra became silent due to Riveting Night's words. In the back of their minds, they had realized that their purpose in The Bazaar was not so simple as purchasing some items.
However, her current words directly implied that they were not to be spectators here, they would be bidders. Since the only items on display currently were various species of slaves, it didn't require a genius to ascertain exactly what they would be buying.
Warm Spring and Sublime Notion shifted uncomfortably in their seats. The idea of purchasing fellow sapient beings like they were chattel rubbed them really wrongly, but it was their sister who was performing the act.
The reason for their hesitation was complex. On one hand, they wanted to directly rebuke this and chastise Riveting Night, but they also knew that whatever the case, this was a game.