User blog comment:Stormjay Rider/The Volcanic and Obsidian worlds/@comment-4706022-20130829005832/@comment-4724333-20130829010207

"Sure, some say that Obsidian comes from volcanos, but I don't think that the "Obsidian" part was supposed to be literal." In other words, I think it's just supposed to be a world full of rock that looks like Obsidian, not necessarily is. And even if it's from a volcano, the volcano could be "long-gone".

Blue Lava... Well, blue is generally a "calming" colour, whereas red is "exciting", and as this is a difficult world, I personally think we should use an "exciting" colour. This doesn't have to be red, I suppose, but then we'd have to explain it in-universe.