[RPG] Are there other modifiers to AC


My knowledge of D&D is primarily 3.5. In that edition, there were many modifiers that affect AC, Natural Armor, Deflection Modifier, Dodge Bonus, Insight Bonus, Luck Bonus, and Sacred Bonus. I have not been able to find any of these rules in any core rulebook. My question is whether or not these are still official rules?

Best Answer

5e doesn't have modifier types

Though most modifiers in 3/3.5e were assigned a specific type and would not stack with other modifiers of the same type, 5e does not have this concept of modifier typing. Modifiers in 5e are effectively untyped, and the only rule about stacking is that bonuses provided by the same source do not stack, as explained by the DMG:

Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. [...] Game features include spells, class features, feats, racial traits, monster abilities, and magic items.

So you can't double an AC bonus by casting the same spell on yourself twice, for instance, but if you are affected by two different spells that both give you an AC bonus, they stack together.

However, there is a caveat. Many effects in 5e confer improved AC by allowing the use of an alternative formula to calculate your base AC, rather than modifying your existing AC - most notably, this is now how wearing armour works. However, as described in the PHB and Basic Rules:

Some spells and class features give you a different way to calculate your AC. If you have multiple features that give you different ways to calculate your AC, you choose which one to use.

Since you must choose one formula to calculate your AC even if effects mean you have a few choices available to you, this is a way of preventing some stacking effects. Mostly it seems effects which would have provided Armour or Natural Armour bonuses in 3.5 now work in this way.

In general in 5e it's harder to get as many bonuses going at once to stack with, because most useful magic items require attunement; typing the bonuses and preventing them from stacking as well would be overkill. This is part of the general simplification of 5e; you might also note (if you haven't already) that 5e has no such thing as a touch or flat-footed AC, where the types of AC bonuses you had were very relevant.