AD&D 1e (in Unearthed Arcana) and AD&D 2e allowed the major PC races to take the cleric class, but for the demihumans, level limits in the rules prevented them from accessing the high level spells. In a setting like the Known World, where all the major PC races have their own nations and cultures, it is a little awkward that the demihuman classes lack religious leaders and the ability to ask their gods for the same favors humans can.
We can assume, as the game always did, that these personages exist, but are left to the NPCs of the world, but I've always disliked the idea that NPCs get options that are not there for the PCs. That is why I present this optional class for Hin “clerics”, originally developed a few years back with my friend Rich Trickey. The Hin (Halfling) Friar, an optional halfling "cleric" class for Classic D&D!
The Hin Friar (236kb PDF)
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