"Combo E (6+): This attack gets Powerful:X . X equals the amount the control check to play this ability was modified by card effects."
OK, does this include negatives? I say yes, other things have before.
Now, does that include negatives AND positives together? Say I have a Shadow Flare (CCs get -1 while in the card pool) whose E I did play and it dealt damage (CCs get +1 for the rest of the turn). Then I play a Wild Storm whose E I did play (CCs get +1 for the rest of the turn).
When I follow with Curse of the Ancient Mariner, and I check, let's say a printed 5, it becomes a 6. Now, X = ?
X = 1-1+1 = 1?
or
X = 1 + (1 into negatives) + 1 = 3?
Powerful:1 or Powerful:3?