"Abbot??!" Cassian's demeanor paled drastically when his brother spoke to Elijah without a veil to hide his appearance. At first, he thought he was imagining things, but after several blinks, it turned out he wasn't hallucinating. Abbot was standing right there, speaking with the enemy, and he still looked human compared to Elijah who's dim red eyes held a tinge of malice.
This means Abbot is still human, but Elijah hates humans, so how does he know Elijah? And why are they here??
With the soft tune of the orchestra being played in the main hall, Cassian couldn't grasp the conversation they were having, but he refused to look away, worried that he might lose sight of them if he did.
Watching them for what felt like minutes, they suddenly parted ways and went in the opposite direction. Elijah slipped his mask back on before disappearing from his sight, and that left only Abbot who continued to walk down the hallway.