Ok, I lied. I was going to tackle these completely in order, but just for some variety I decided to start Natas to see what kind of challenges it had. After some investigation, these appear to be web based. The first challenge tells us that the password can be found on the page itself. A quick ctrl+u, and we see that the password is embedded in the source.
<body>
<h1>natas0</h1>
<div id="content">
You can find the password for the next level on this page.
<!--The password for natas1 is XXXXXXXXXXXXXXXXXXXX -->
</div>
</body>