my bet is that either omorfa, or some khemian higher up who doesn't want the alliance (i want to suggest the vizier but that would be very cliche and we already did that with cato), was behind the assassination attempt.
i highly doubt it was the teacher. he may be bigoted about sexuality and gender, but he seems to want the alliance. one of the scipio letters on patreon is about how scipio had to talk veteris out of painting khemian tattoos on himself before a meeting bc he thought it would honor the khemians without realizing it'd be insensitive. veteris seems to really want scipio to spy on neferu, which scipio can't do if he and neferu are dead.
brunis hasn't had enough screentime yet for me to speculate much about him, but with how well the khemians supposedly treat their uplifted children, i'm not sure what his motive would be
Edited at 2020/08/03 09:14:07