Yeah, I get that - I'm just not sure why the differences between a claw and a bit (usually, what, a damage type, maybe, apparently some reach, and sometimes a breath-related damage bump) is enough to make a claw and a bit "feel" different enough to bother with looking at two different lines on a statblock when your damage roll will probably make a bigger difference on the damage differential.
the neck has a longer reach than the arm, that is where the 10ft come from, one does pierce and fire for an average 26, the other slashing for an average 15 (using the red dragon here)
Could there be more differences and could the two be more interesting, sure, but Rend does the exact opposite of that.
I grant you that it makes the narrative more flexible, by not referring to any particular attack, but if you can describe a Rend as ‘whatever’ you could have done that with the Claw too, no one forced you to always describe it as a claw attack
I guess I was hoping you'd share more specifically why you can't think of a good explanation. I assume that for some reason, you don't like the idea that they spit it, shake it off their scales, conjure it with magic, or simply corrupt the area around them (those are just four off the top of my head, without actually looking at the ability.
magic explains everything and nothing, it is my least favorite explanation because of that.
Spit is the only one I find halfway acceptable, which is why I mentioned it some pages back.
Shaking it from their scales does not explain why the AoE is up to 90ft away from the dragon.
Corrupting the surrounding does not explain what triggers the miasma in a certain spot.
I might be able to come up with more if I see exactly how the ability works, or I might scratch one or two of those out, I'm really not sure exactly what the ability is that you're objecting to).
it’s a reaction to the dragon using a legendary resistance or the dragon being hit by a ranged attack. At that point the miasma appears in a 30ft radius up to 90ft away in an area the dragon can see.
Deals poison damage, save halves
It doesn’t say how it works, only what it does
Spit is the best I came up with, not really a miasma though nor does it require the dragon to see that area imo (could be behind a wall)