Small vs. Very Large

[Steve Lewis]

So, a random situation just popped in to my head, and I'm curious if there are any rules that would address this:

While it's rare for a particularly large creature to have dex bonuses to AC, it _does_ happen. What I wonder is...if a sufficiently small creature is in close enough proximity, (a halfling on a dragon's back, for instance), would that circumstance be enough to negate the dex bonus to AC, or does the RAW with regards to dex bonuses to AC take such a situation into account when deciding on the bonus?

[Fuzzy-Wuzzy]

Steve Lewis wrote:

While it's rare for a particularly large creature to have dex bonuses to AC, it _does_ happen. What I wonder is...if a sufficiently small creature is in close enough proximity, (a halfling on a dragon's back, for instance), would that circumstance be enough to negate the dex bonus to AC,

Not under RAW or RAI. You could always make it a houserule, of course. Or a feat for the small creature.

Steve Lewis wrote:

or does the RAW with regards to dex bonuses to AC take such a situation into account when deciding on the bonus?

I think it's not so much that they considered every possible situation as that they want the rules to be reasonably simple.

EDIT: BTW, the true power of such an ability/rule wouldn't be about the dragon's actual dex bonus, it would be that denying it its dex bonus (whether it has one or not) qualifies it for sneak attack.

[arkham]

Size bonuses and penalties to AC and to-hit take care of that concept.

[ErichAD]

In the Champion's Mythic selection is an ability called "Titan Bane" which provides this benefit. When you're in the space of a creature 2 sizes larger than you, you gain cover against their attacks and they are flat footed against your attacks.

[Tacticslion]

Also, while third party, there's always this template - it doesn't directly apply, and, as noted, it's 3rd party, but it's a fun bit of rules extrapolation, for those who are interested in applying it in other situations.

[SheepishEidolon]

The mouser archetype of the swashbuckler allows flanking from within the space of a bigger creature.

[Bob Bob Bob]

Rogue archetype.

Limb-Climber wrote:

When adjacent to or in the space of a corporeal creature at least one size category larger than herself, a vexing dodger can climb that creature’s body with a successful Climb check against a DC equal to the target creature’s CMD. Although the vexing dodger is holding on to the creature, this action isn’t a grapple; it doesn’t provoke attacks of opportunity from the creature, and neither the vexing dodger nor the creature she climbs gains the grappled condition. While the vexing dodger is on the climbed creature, the creature takes a penalty on attack rolls against the vexing dodger equal to the number of sneak attack dice the dodger possesses.

This ability replaces trapfinding.

So it's a penalty to attack, not AC.