First time owner help please

[WNC]

In ANY event, unregulated heating is a huge no-no...if you snake gets burned it's horribly painful, slow to heal & potentially fatal.

^ I second this. Never put a snake in an enclosure with heating sources without regulating them first.

As for the stain, it looks precise to me. It looked as if he slithered through a dirty tube and got dirt on both sides. Is the inside of the log dirty at all?