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 found this build a while ago and after using it I found it to be a pretty good build.
When using you get around 1K+ ability power, enjoy the pwnage :)
I did not post a "full guide", this guide works with fine with the information I gave you.
Feel free to drop questions.
For runes I use
9 x Greater Seal of Potency (+0.59 ability power per seal)
9 x Greater Glyph of Potency (+0.99 ability power per glyph)
3 x Greater Quintessence of Potency (+4.95 ability power per quintessence)
9 x Greater Mark of Insight (+0.95 magic penetration per mark)
You want your drain skill to hit well, I use magic penetration to help with that.
The rest is just for extra ability power, you could switch some for mana/health.
Whenever you encounter an enemy the first thing you want to do is harass them a bit.
Once they are 3/4 health approach them and use your fear skill on them, then follow up with drain, repeat this process untill they are dead.
If you for any reason get low on health retreat and use your drain skill on cannon minions to get back on health.
Late game, one of the tactics you could use for group fights is hide somewhere close to the enemies in a bush and then use your ultimate, fear the squishy enemy and maybe drain them at the same time your ulti is damaging them. With this build I showed you you will have 1k+ ability power which means you do sick damage!
Keep in mind that without mana you are nothing, and you are NOT a tank, some people believe Fiddle is a tank, I think the opposite, you are mana depending, without it you die very easily. Keep that in mind.