Confused

[{PK} Unfair]

It may just be me missing something, but I can't figure out how to get out of the second level. I don't see any stairs, and it said something about finding one of two altars. I assumed those were the portal-looking things I saw when I entered, but they disappeared once I walked into one.

I did get a new spell at some point during massacring all the enemies, but I didn't notice if it came from the portal or during a different level-up. Did I break the level, or am I just missing something that should be blatantly obvious?

Edit: And I did run around the entire level looking for places to use my new spell, but no squares were highlighted that I noticed.

[Ratz 'N' Godz]

Auto explore (E) should take you to the nearest point of interest (unexplored part of the level, altar, etc ...), or if everything have been explored, to the down stair.

Altar grants you a bonus in a magic affinity, so it can unlock a new spell, as well as spending experience in a magic skills, so I can't tell which one was the reason.
But no spell is required to advance