The concept of a clerical domain based on the Mists of Ravenloft is one full of potential and of which I was excited to read. While the domain presented here appears to be mechanically sound, the flavor and supporting information is severely lacking. Here's why:
The introduction to the Mists domain focus entirely on the Church of Ezra’s sects and hardly provides enough information about any one of those sects to make it worth it. This is also the first point in which the author references outdated material from the 2e/3e Ravenloft campaign setting.
While the domain spells can be considered appropriate for the Mists, the bonus proficiencies of martial weapons and heavy armor seem to be more of a reflection of Ezra as a guardian and protector.
The theme of mist plays only a cursory role as a visual effect in the first Channel Divinity power, entitled "Shield of Ezra" – again focusing here on the deity rather than the Mists.
The second Channel Divinity power, while specifically related to the power of the Mists, was designed with the 2e/3e Ravenloft campaign setting in mind. For the uninitaited, and those playing in the modern 5e version of Ravenloft, will likely find little to no context for this power.
Finishing out the document is a write up for the divine Ezra herself. As a goddess of healing and protection who is fighting the go fight on behalf of mortal men (which isn’t really reflected by her alignment), she is quite bland and uninspiring. The only connection she has with the Mists of Ravenloft was to sacrifice herself to them in order to achieve godhood – and the reasons for that aren’t even explained. Under suggested domains, it lists Life, Mists, and Salvation; the last of which I’ve never heard of in 5e D&D and there is no reference provided as to where I might find it. The only thing of worth about Ezra is her symbol – it is simple yet eligent!
Overall, the material presented fails to focus on what its title promises – a domain centered around the Mists of Ravenloft – and instead provides information about a bland and nebulous religion that fails to engage the reader’s interest, and references to the defunct Ravenloft setting which have not [yet] been brought forward to the new edition. I give it two stars solely for the fact that a creative reader, if so inclided, could use the information presented here as a seed for a new deity and/or religious order in their own game.