Crystal Maiden is a ranged intelligence support hero. She is a fantastic lane support with abilities that make her a strong ganker and harasser. Above all, you should support your team, purchasing the Courier and Observer Wards and other utility items.
Skills
Max Crystal Nova first, use it to harass in the lane and to provide AoE slow and damage in teamfights.
Get a point in both Frostbite and Arcane Aura early on, then max one of these after you've maxed Nova.
Typically you'll want to max Frostbite before Arcane Aura but some line-ups will get more out of you maxing the Aura.
Always get your ultimate, Freezing Field. Successive patch buffs have made these tremendous for providing AoE teamfight damage and slow. Try to use only after the enemy team have expended their stuns.
Items
You are farm independent, so purchase items that provide utility for your team such as Observer Wards and Force Staff.
Starting Items: Courier, Observer Wards, Tango, Healing Salve, 1x Branch.
Core Early: Flying Courier, Observer Wards, Boots of Speed, Magic Stick.
Core Mid: Observer Wards, Tranquil Boots, Magic Wand, Bracer.
Luxury: Mekanism, Drums of Endurance, Force Staff, Black King Bar, Aghanim's Scepter, Heaven's Halberd, Scythe of Vyse.
Situational: Sentry Wards, Smoke of Deceit, Dust of Appearance, Gem of True Sight, Hand of Midas, Pipe of Insight, Ghost Scepter.
