The return of Cohen...
It's been 6.4 years since a small group of survivors fled the Blood Machines. In awe of their power these tribal settlers became tech-worshipers and vowed to leave behind their weak flesh and ascend beyond the confines of limited humanity.
As the years pass their learning grows, they discover electricity, machining and finally the ability to create bionic and prosthetic augments. The societal leaders have a regime of implants but all colonists get at least one, the most common being venom fangs.
Colony discovers the Archonexus, and works towards this goal. Eventually the core societal and spiritual leaders leave to found a new colony in search of this prize.
A year later a raider attack comes... Cohen, wife of Bren, senior builder and colony member since the beginning arrives in the attack group, they try to take her alive. She dies fighting but not before giving many colonists of the new settlement toxic bites from the very prosthetics that they, themselves installed.
TLDR: former colonists can use your own enhancements against you!