Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Veigar as ADC is early game really weak, so just stack ur Q until u have ur Sheen. Then begins the Fun. Just stun the enemy ADC make Q and AA once or twice. That is a really good poke where the enemy ADC cant do **** against.
Now u should have Trinity, Boots and maybe Essence Reaver. With that items, u have really hard burst and sustained damage. Just dont forget to stack ur Q.
In late game its just gg. U can 1 shot the enemy Midlaner or ADC and shredder theire Tanks with ur AA`s. Bruisers cant do **** because of ur stun. Just dont go 1v5 like an ideot and the game is won.