Huskar is a strength carry.
He is ranged with a
Pros / Cons / Averages
High damage skill: Burning spears
High attack speed and extra damage from berserkers blood
High heal with inner vitality
Snipes away a lot of health from a tank
Damages himself when he attacks with Burning Spear.
His ult takes away 35 / 30 / 25 % from his current health
Needs a lot of farm to be really effective
You need to know when to go in
Decent movement speed
As starting items you want a build up to magic wand and urn of shadows.
The item order is this: Boots of Speed, Urn of Shadows,Power Threads Magic Wand, Armlet.
After that get luxurary:
Black king bar against a magic heavy team.
Monkey king bar if you have other survivability items ( the high attackspeed helps the proc)
Assault cuirass if you need more attackspeed and armour (you need it late game)
Heart of Tarrasque for survivability
Aghanhims Sceptre is a nice pickup, it increases the damage of your ult to 65% of the opponents current health and decreases the cooldown to 8 seconds(!)
Max Burning Spears first, you need it to harass the opponent and deal out a ton of damage when you actually try to kill them.
Berserkers blood is your skill you want to have when you leap in with your ult.
Your hp is lowered very much, at that point you want the extra damage and attackspeed.
Burning spears stacks with itself. If you have 10 stacks (very possible thanks to bersekers blood) it will deal 160 damage per second. That equals Doom from Doombringer.
Your inner vitality is used for healing. It is advised to use it on <40% heroes, it will heal more then.
Your ultimate is a great 1v1 killer skill. You sap away 50% of the opponents HP and fuel your own berserkers blood.
For the first 5 levels:
You need a lanepartner to kill, a stunner is best.
Just autocast burning spear, let it stack some and grab the kill.
Use your ultimate and autocast burning spear to get some stacks in.
Use inner vitality first, then ultimate, then armlet (for the hp boost) and start attacking with burning spear.