Hydrogen deficient carbon (HdC) stars are a rare class of supergiant variable star with less than 1% hydrogen by mass. They exhibit a wealth of exotic characteristics such as production of dust, carbon-rich atmospheres, anomalous isotopic ratios, and very low metallicities. The most likely explanation for their formation is via a low-mass white dwarf merger, namely a CO-WD + He-WD merger. In this talk I will present the evidence that we see for this exotic formation mechanism, such as the oxygen isotopic ratio, our efforts in stellar modelling, and population synthesis modelling. I will also provide an overview of their unique characteristics and pathways for current work on them, especially regarding dust production, variability, and our current understanding of their kinematics using Gaia data.