Gargoyles are good against air, but they suck against ground units.

Ghouls are good if you know how to use them... try clicking on trees that are behind an enemy's hero. This will make it so the ghouls walk over all the units in front of them and when you reach the hero, click on it and watch him die. (This is called force walk)

You should also try www.warcraftstrategy.com for strategies.

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