Actually, more so than adding and augmenting, I think some taking away is in order. I'd have been far more interested in the menagerie of monsters if it was presented in a more vague and mysterious fashion. Rather than "here's exactly what they look like and here's a comprehensive list of their strengths and weaknesses" ... a sense of danger, for me, is created through [i]not[/i] understanding our enemy.

Plus, it makes sense on a mechanical level. The only way for us to know anything about these monsters is if people have survived encounters with them, come back, and told the tales. Which, if there are enough survivors to paint such a clear picture on how they fight, then how dangerous could they really be?