After entering in 129 Armour Classes from the SRD into my spreadsheet, I’d gotten as far as “G”, so I realised there were a *lot* of monsters in the core D&D 3E monster manual!
However, it was about the same number of monsters I’d added as part of the Monstrous Compendium Annual, so I decided to create some charts from the information so far. It should be noted that I left out Dragons altogether in this data, but Devils, Demons and Elementals (the major high-level threats) are included.
This is what I got:
So, that’s the count of Armour Classes for each value. It doesn’t really tell us all that much, except to say there are some very high Armour Classes, but most of the ACs cluster around 15-18 – a 2-5 in AD&D terms.
Slightly more enlightening is this look at ACs by Challenge Rating:
Let’s have a look at just CRs up to 10:
There’s still a pretty wide variance of ACs on each Challenge Rating. The trendline is, as usual, not the most accurate but does show an increase as the range increases.
One thing that is evident when compared to AD&D is that “negative” armour classes – that is, ACs of greater than 20 – are more common in 3E. They’re still not dominant (as far as this information goes), but as more monsters were made for the system, and especially in the reset of 3.5E, I seem to remember that having a very good AC became more of a thing for high-level monsters.
3E owed a lot of its lineage to AD&D, and was more respectful of its heritage in a lot of ways than 4E was, but the design decisions would mean that attack bonus increased every level faster than any other edition.
I do need more data, however, so it’ll be back to data entry in the near future!