If you are a newcomer for this class you need to know this.

1. He is really hard do play
2. From beginning he is so weak and he doesnt have Health
3. Step back from your opponents
4. He need to be calm unless he gain level 10 (R)
5. You need to be patient for Hero (Class Level) 4
6.You are able to Youngle after level 8 (Solo)

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You should have some Experience with this class if you are level 4 so all things from level 1 are still true but now you have more power. For level 4 I recommendedthis because he will have more power for beginning. Remember Illidan is a late game Hero so just run on a map and PvE (Most like Youngler). If you gain level 13 then you are able to be more dangerious for your opponents. If you are level 20 then just fly around the map and kill everything.

Dont Forget:

1.Late game Hero
2.1v1 or 5v5 (best)
3.From beginning he is weak (low HP too)
4.Dont Die !