What is the most important Beorn gives about Mirkwood forest?

From the text:

But your way through Mirkwood is dark, dangerous and difficult," he said. "Water is not easy to find there, nor food. The time is not yet come for nuts (though it may be past and gone indeed before you get to the other side), and nuts are about all that grows there fit for food; in there the wild things are dark, queer, and savage. I will provide you with skins for carrying water, and I will give you some bows and arrows. But I doubt very much whether anything you find in Mirkwood will be wholesome to eat or to drink. There is one stream there, I know, black and strong which crosses the path. That you should neither drink of, nor bathe in; for I have heard that it carries enchantment and a great drowsiness and forgetfulness. And in the dim shadows of that place I don't think you will shoot anything, wholesome or unwholesome, without straying from the path. That you MUST NOT do, for any reason. "That is all the advice I can give you. Beyond the edge of the forest I cannot help you much; you must depend on your luck and your courage and the food I send with you. At the gate of the forest I must ask you to send back my horse and my ponies. But I wish you all speed, and my house is open to you, if ever you come back this way again."