Do 1st Edition (OD&D) subclasses replace their class, or add onto their class?
Note: This is for OD&D (the original box set which came out in 1974), not AD&D.
In OD&D, Monk (which debuted in the Blackmoor supplement) is called a subclass of cleric. Does that mean they get cleric spellcasting? The supplement doesn't say whether the cleric features are added onto the monk features, or if the monk subclass is replacing the cleric class wholecloth.
Re: Do 1st Edition (OD&D) subclasses replace their class, or add onto their class?
Not perfectly certain, but in AD&D Ranger was a subclass of Fighter, Druid was a subclass of Cleric, etc. and Druids didn't count as Clerics for any other game rules. As such, I suspect the same ideology applies to OD&D, so Monks are just a distinct class, related to Clerics but not subject to Cleric rules. Kind of like a second cousin.
- M
Re: Do 1st Edition (OD&D) subclasses replace their class, or add onto their class?
No, the class gets just its features.
Re: Do 1st Edition (OD&D) subclasses replace their class, or add onto their class?
I am more familiar with 2e, but subclasses are their own class. Clerics and Druids are both sublcasses of priest with their own progression, spellcasting and rules. Same for Thieves and Bards being subclasses of rogues.
What you are thinking of (additions to your class that add features in exchange for other features) are known as "Kits" from the complete books. Specialty priests to particular deities are also a kind of kit in this way.