I will outline the subject of a forthcoming report, which argues that: i) a world of advanced multi-agent systems is coming soon, including in high-stakes situations; ii) these settings present qualitatively different kinds of risks to the single-agent case; and iii) not enough work is being done on this right now, but there are lots of ways to make progress. In so doing, I will identify several key failure modes and risk factors, and provide multiple concrete examples. I will conclude with a set of priorities for future research.