The Dungeon Master’s Guide has rules on making Monsters for 5e, but the monsters in the Monster Manual don’t match up to those criteria at all, mostly because both books were being written at the same time.
Angry GM’s Monster-building articles
There’s some evidence that the monsters in Volo’s and Mordakainen’s Guides are closer to the DMG math.
I’m going to add to this and try to make it more of a guide, try to apply a pedagogy with steps incrementally introducing concepts a player might be familiar with but in the context of the design framework behind the game. Including things like damage by class and level so the monster hit points and armor class make sense.
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