Hello, everybody, welcome to my guide. My name is the handsome man. I am by no means an expert at using Diana. As of now (as I start the guide) I am level 25 with about 125 or so wins. I am not going to tell you how to play Diana, but I will tell you how I play her and why. I bought her and the skin bundle the day she came out, and have been consistently playing as her since (it is currently 8/20/12). I have been doing quite good, and while I am not an expert in League of Legends, I am always improving. So welcome to my guide for Diana, Scorn of the Moon.
Good AP ratios
Her Dark Valkyrie is easily the best skin in the game
Crescent Strike is odd to dodge
Lunar Rush amazing
Damaging shield that refreshes with more damage done
Can pull enemies into her damaging shield orbs
Effective in ganks as well as team fights
Has little to no escape, aside Flash
Gets blamed for KS a lot
Flat Attack Speed is best, due to her passive. Nothing else really goes as well. Her passive is very nice, but don't actively rely on it to be your damage dealer, it's good for your dead time though, when all spells are on cool down.
Flat Ability Power is best, because Ability Power is her main stat. I take the flat glyphs instead of the scaling one because she needs the damage early game to start snowballing, and by late game she is already strong enough to completely melt people, she doesn't need the few extra Ability Power as much as she needs it early game.
These are defensive, I just split Armor and Magic Resist to get some balanced Defensive Stats.
Usual Ability Power masteries, nothing really special, again splitting the Armor and Magic Resist points in the Defensive tree. I take the Flash cooldown in Utility tree because Diana has no escape aside from Flash, it also helps her get in range if for whatever reason she can't Lunar Rush, Crescent Strike or needs to get in range for any ability.
Boots: Pretty basic
Potions: 2 Health, 1 Mana. Health potions are pretty basic, lets you stay in lane longer, and Diana is pretty Mana hungry early, so the Mana potions are needed as her damage comes from spells (and a little bit from passive)
If you can help it, don't Recall (B) until you have enough money to buy a Needlessly Large Rod. The Needlessly Large Rod allow you to massive amounts of damage due to her strong Ability Power ratios. I normally am about level 6 when I can afford this, so it goes well with Lunar Rush you will be getting at that point. Then get your Blasting Wand, then finish your Deathcap. I usually get this around level 10 or 11.
YES IT IS A LONG TIME TO GET TIER 2 BOOTS, BUT THE DAMAGE YOU GET SO EARLY MAKES UP FOR IT. WITH PROPER MASTERIES, YOU SHOULD HAVE AROUND 200 OR MORE ABILITY POWER BY THE TIME YOU GET YOUR RABADON'S DEATHCAP, AND YOU MELT PEOPLE WITH THAT MUCH ABILITY POWER SO EARLY.
The Next Step, The Next Boots:
Upgrade your Boots of Speed into Sorcerer's Shoes. Pretty basic for an AP champion.
Third Item, Being a Heartless Lich:
Lich Bane should get you up to or past 300 AP by this point, and gives you other good stats, but you really get it for the passive. Diana has low cooldowns and spams her abilities together a lot, and her Lunar Rush is relatively spammable, so the added Ability Power after your Abilities is great. It add's a lot of not-active damage between the damage from Lich Bane's passive and Diana's passive.
Fourth Item, Here's Where The Options Open:
This item is very situational, and it really depends on how the game is going. Choices are between Abyssal Scepter, Archangel's Staff, Rylai's Crystal Scepter, and Will of The Ancients.
Fifth Item, Their Health is Abyss:
If you didn't get an Abyssal Scepter as your fourth item, get it now. Good Ability Power, good Magic Resist, and lower's enemies Magic Resist in an aura, which is helpful as you're a melee Ability Power champion, and you're up in their face a lot. By this time they should definitely be getting Magic Resist to counter you, because you will be destroying their health bars quickly, and this sort of counteracts their efforts.
If you did get an Abyssal Scepter as your fourth, I'd suggest trying a Rylai's for the slow, although the slow is only needed if they're stacking to counter you.
Final Item, Again, Optional:
If they're very healthy, get a Deathfire Grasp.
If it's going to go a lot longer, get an Archangel's Staff
If your team is useless without you, get a Guardian's Angel
If they're actually smart enough to focus you and you don't have it, get Rylai's Crystal Scepter
They usually have some health by now, so I get a Deathfire Grasp in most occasions. It will wipe out around half their current health, so use this to open up on a full health target (but only if they have stacked enough health that you cannot kill them in one burst, so use this if they have champions like Dr. Mundo (use this on him, and follow up with your ignite to cut his Ultimate's effectiveness))
How to Play
I usually go Bot (I hate jungling) Lane until level 6/when you get your Needlessly Large Rod. At this point, leave lane and try to gank wherever needs it, especially if there is no jungler on your team. Try to make the enemy team uneasy. START ROAMING
Keep your eyes on your map. Map Awareness is key. If the enemy mid champion is Recalling (B) under their tower, you can go in the jungle by their tower, and Crescent Strike > Lunar Rush and kill them quickly, and then Flash over the wall if you're afraid the tower will get you. Diana can turret dive/ turret gank very well when Flash is up.
Late game: Focus their highest damage champions, you are squishy. You do enough damage to crush them quickly, especially with your team assisting. Your Deathfire Grasp and Ignite combo is very good on tanks, especially Dr. Mundo. Stay with your team, you're to squishy to be alone.