Despite promising electrochemical stability and sometimes promising ionic conductivities, Li 3 OCl is a hygroscopic and air sensitive material. This has raised numerous questions on the legitimacy of Li 3 OCl as the true composition, with concensus trending towards the fact that Li 3 OCl being a hydrated form (Li 3-x OH x Cl) or even Li 2 OHCl. In a critical review by Rettenwander and coworkers , they point out the fact that typical syntheses of Li 3 OCl uses LiH, H 2 O, or LiOH within the synthesis, thus it is inevitable that H/OH will be present in "Li 3 OCl". All may not be lost, however, after several experimental and computational studies show that a hydrated composition may be to the advantage of the ionic conductivity, as rotatable OH units enhance the mobility of Li-species in the material. Ultimately this may come at a cost, as the conductivity has been shown to be highly correlated with the proton and lithium vacancy concentration , and controlling the amount of hydrogen in a hygroscopic material is difficult at best. Whilst computational studies exist on the intrinsic defects of Li showed to enhance the ionic conductivity of Li 3 OCl. Squires also showed that undoped Li 3 OCl could expect equilibrium ionic conductivities of ∼ 10 -10 S cm -1 , significantly below experimental observations. Here, we present full intrinsic and extrinsic (H) defect models for metastable Li 3 OCl, calculated with the hybrid functional HSE06. Using the quasiharmonic approximation, the chemical potential stability region of Li 3 OCl is shown to exist from ∼ 750 K and shows that when undoped, Li 3 OCl displays two types of Schottky disorder: full disorder under Li-rich conditions, and Li 2 O disorder under Li-poor conditions. Hydrogen is shown to incorporate very easily, in line with the hygroscopic nature of Li 3 OCl, and suppresses these Schottky defect clusters. Additionally, lithium substituted hydrogen is likely to relaxe offsite to form OH groups and induce a "pseudo-V Li ". Accounting for this defect in a conductivity model reproduces experimentally observed values.