Stones :
- "can be targeted or affected by monster and hero attacks."
- "can be affected by conditions, automatically fail attribute tests and may use their action to perform an action printed on a Condition card (e.g. to remove Stunned, Bleeding, and Burning)."

Just to be sure :
they are immune to cards / powers like :
- Dark Charm
- Pit Trap / Grease Trap
- Word of Misery
in short any card that says "hero"!

But also any card that says "figure" like :
- Explosive Fall (Tristayne Plot)
- Fire Gems (OL Reward)
etc

I'm right till there ?

Then ... what about cards like Critical Blow and Flurry
They are used to attack, ok, but they specify that they can be used "[..] when a monster attacks a hero [...]"
.. by the rules I would say Stones are not hereos so we can't cards like these !

same thinking with the power (and the like) Sweep from the Giants
it's special attack "Perform an attack. This attack affects each figure within [...]"
again by the rules Stones are not figures.. so again, I would say that Stones can't be attacked by such cards / powers...

What, you out there, think ?
Is there some answers from FFG specifying something one way or the other ?

I don't have an FFG answer.

I would say they are affected by all attacks (including monster and hero abilities that include attacks, like Sweep or Leap Attack, even though they "affect figures") based on that sentence in the LotW rule book.

But yeah, I actually can't think of an OL card that would affect them.