No, it multiplies the damage instead of increasing the base attack.
Are you certain? I'm not.
Yes, in most definitions of prowess it literally says “multiplies damage by x% for x amount of time( or permanent in some cases)”
They say "increases special [attack] damage by X% ([no time limit] - CAIW and recoil mastery or [for Y seconds] Proxima and others or "until special attack ends" for Havok).
From the discussion regarding recoil, it should work the same way and tack on X% of base attack to the special damage. Which can be a lot or a little depending on the champ.
Comments
Are you certain? I'm not.
Yes, in most definitions of prowess it literally says “multiplies damage by x% for x amount of time( or permanent in some cases)”
They say "increases special [attack] damage by X% ([no time limit] - CAIW and recoil mastery or [for Y seconds] Proxima and others or "until special attack ends" for Havok).
From the discussion regarding recoil, it should work the same way and tack on X% of base attack to the special damage. Which can be a lot or a little depending on the champ.
5 prowess = double damage (+100%)
10 prowess = 3x damage (+200%)