So whenever you have a TF/Sheen and you press your Q, it procs Sheen/TF. When you actually hit someone with it, it consumes the Sheen/TF proc.

So my question is, what is the atk dmg benefit you get from it, exactly? Does it increase the damage of the skill, similar to how Sheen works on GP's Parley, or is it just your basic atk dmg is increased to 100% and then it adds on Talon's Q damage?

I'd assume the latter, but maybe someone knows for sure.

The proc adds your base AD to the attack as bonus damage. If you have 100 base AD, then 100/150 bonus damage is added on to the damage calc, on top of your total AD + the bonus damage from the skill. The bonus damage doesn't count for crit damage - if you crit the Q then you still only get 100/150 bonus damage added.

It works the same way on GP's parrrley.

according to League Wiki sheen/TF bonus is based on the champions base damage. IE starting damage without items plus what the champions naturally gains as they level. unless a item or ability specifically boosts base damage then it is not factored into sheens bonus damage. talon has ~50 base damage at 1 and gains ~3 damage per level. he has ~100 base damage at 18 to at max your getting 100 bonus damage from sheen or 150 damage from TF. sheen/TF are not effected by crits btw.

off of this info i am left wonder why exactly people pick up this item on talon.