It definitely does need to be shown in game.
As for what it all does, see below:
{quoted}
Not even the wiki accurately tells you everything.
What it does is increase everything about the ability by x% with some exceptions.
So:
- AD ratios on spells by extension of spell damage being increased
-
- (Voli/Rengar/Draven/etc.)
-
-
- This is why you see Dravens with double Rageblade, it's not just for the attack speed
- True Damage
-
- (Vayne... can't remember if Morello or Red do true or spell damage but they're increased too, unsure about Demon true damage)
- Healing
-
- Shielding
-
- Bonus Health
-
- (Lulu... idk about Origin/Class bonuses though like Brawler and Shapeshifter)
- Bonus AD
-
- Damage Reduction
-
- (Braum... I think that's it?)
- Item damage if they deal spell (magic) damage
-
- (Ionic Spark/Ludens/Statikk/etc.)
What it doesn't affect:
- Target numbers
-
- (Number of Karthus ult targets, etc.)
- Range
- Duration
- CC
-
- (Including Anivia's AS slow)
Exceptions to the above:
- Yasuo's shield does not scale with spell damage (as of last patch)
Things I have no clue if it affects:
- Attack Speed bonuses
-
- (essentially just Rengar's bonus AS)
- Crit Chance increases
-
- (essentially just Rengar's again)
- Kindred's minimum health on ult
- Evelynn's <50% health multiplier
-
- (it increases all damage due to the base being affected, but idk if it affects the multiplier as well)