The sinthral are a race of monstrous half-human half-spider creatures who inhabit portions of the Rift and perhaps other remote places on Mars. The legendary lost tribe of Brecknar is said to worship the spiderous sinthral and make them human sacrifices.
To the Muvari Tribe, the idea that the life of a tribal member would be esteemed at so little value is revolting. So to the Muvari, to suggest someone be made a sacrifice to the sinthral is to suggest they are utterly worthless to their tribe–an insult of paramount gravity.
Quote from Ntashia: “You weren’t invited to take part in this conversation, and I’d suggest you back off before I slit your throat and throw your carcass into the Rift as an offering to the sinthral.”