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.
I've play tested this build a bit, and it works quite nice for me at least. The item set is a bit different then some of the builds i've seen and i'll explain my choices. First is the Sheen, which is a must for evelynn, the bonus damage from popping out of stealth and the spamming of hateful, makes her physical really powerful. Zeal for the movement and attack speed, the crit helps, but mainly going for triforce. The boots are optional, i like the magic pen to help on tanks but the Boots of Mobility can go there instead for getting around faster. Manamune is an item i haven't seen on alot of her builds, which is surprising. It provides great mana and mana regen to spam hateful after stealth, and the bonus to damage from her max mana increases it further. Guinsoo's Rageblade, ups the AD/AP and increases the attack speed. Stealthing alone gives two stacks when triforce procs, so when you ravage its up to 4 already, and spam hateful, super fast attack speed as well as uping the damage on hateful. Malady is very helpful. It will push her to 2.5 attack speed with the rageblade as well as increase her ability power alond with the magic resistance reduction on the target to further increase her abilities. The last item is to help even out the AP side of Evelynn, but depending on the situation, a BLack Cleaver would fit nicely also. However, if you plan to put Black Cleaver in remember to trade out the RageBlade for a Last whisper. Reason being the attack speed cap will be reached, and you won't need the rageblade. So switch it up for some armor pen and AD. Test it out and tell me what you think.