The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z = 3.55$

The James Webb Space Telescope (JWST) has revealed a large population of massive black holes (BHs) in the early Universe with unusual properties which mark them as distinct from low-redshift active galactic nuclei. Such findings have prompted the development of new models of BH formation and growth, and of their co-evolution with host galaxies. Linking the gas-phase metallicity of BH environments to seed masses is key to understanding which evolutionary pathways could explain the population of JWST-discovered BHs. We present new high-resolution JWST NIRSpec/IFU observations covering the rest-frame optical emission lines of a Little Red Dot (LRD) at (Formula presented), known as The Cliff, from the ‘Red Unknowns: Bright Infrared Extragalactic Survey’ (RUBIES). We find evidence for low metallicity ((Formula presented) ) based on the low narrow-line [O iii](Formula presented) 5007/ (Formula presented) ratio, supported by the non-detection of low-ionization emission lines such as [O ii](Formula presented) 3727,3729 and [N ii](Formula presented) 6548,6583. We find that the observed properties of The Cliff, including its overmassive BH, can be reproduced by some simulations of BH growth and evolution down to (Formula presented). However, such outcomes require high seed masses ((Formula presented) ) and appear rarely within a simulation volume comparable to the (Formula presented) RUBIES volume, highlighting the unusual nature of The Cliff. Future simulations and numerical models will help to uncover how such a metal-poor system managed to develop a massive BH and persist to such low redshift.