A: There is a distinction between 'Double Damage' and '2X' damage. I understand the confusion but they are separate game terms which we spelled out in the 2.0 rules sheet and in clarifying text on the updated cards to try and be clearer. I'll post this on our FAQ though since the rules do not appear as a single 'group' of rules on the sheet.
From the 2.0 rules: "“Double” or “Doubling” damage means rotating yourAttack Card to the next highest value. If there is no otherhigher value, it cannot be “doubled” further. (Note: The 2X modifier on ‘Slip Behind’ is an exceptionand does not rotate the card it modifies, see “Riders”.)"
Then later, in Riders....
"Note: a single Attack Card may have multipleadditive Riders, but only one multiplicative Rider.Example: After playing ‘Double Strike’, a playerwho plays two ‘Focus Strengths’ can add both tonext Round’s attack card – but two ‘Slip Behinds’would only allow one 2x modifier."
So, how do we handle 'Potion of Strength' as an example? Potion of Strength doubles damage by rotating the attack card to the next highest number (stated as such on the updated card). If that attack had a 'Slip Behind' rider on it, it would then give a 2X modifier to the total attack value. '2x' the 'double damaged' attack.
However, it would be illegal for Potion of Strength to 'Double' a character's special attack because, the card does not have a higher value to rotate to. And, as quoted from the rules, two Slip Behinds only deliver a single 2x modifier.