Haunted said:
They're relatively rare and really weak, though.
Slimes tend to be more annoying than the outright dangerousness of creepers and skeletons. They're extremely noisy, and they're pretty easy to kill. When they do spawn, though, they tend to spawn in LARGE numbers and can easily overwhelm you. The other problem is that the small ones don't make any noise, and although they can't hurt you, they can nudge you around, which can be dangerous when one sneaks up on you while you're trying to harvest lava
Lava doesn't burn through dirt and stone, so any moat with that as its bottom layer should keep the lava in. I don't have much experience with lava myself though, maybe some of the obsidian artists here who have experimented with lava behaviour can help you out there.
Ok, properties of lava that I can think of off the top of my head:
- It behaves in a similar manner to water in that it will stop spreading along a flat surface after a while, and will keep spreading if it drops down a level. However, it doesn't spread as far as water will before stopping (it's either 2 or 3 squares).
- It'll ignite any block made of wood. It will also destroy any item dropped into it (so dying in a lava pool means that a good deal of the stuff you're carrying will be lost for good.
- While you don't need to surround it on the diagonal to contain it, it can still hurt you diagonally, and it can ignite things diagonally. While I was making my obsidian building, I regulary saw pigs and cows come up to the mold for the obsidian I was casting, and they would burst into flames when they stepped into the square diagonally from some lava.
- Lava flows and stops flowing much slower than water. If you accidentally tunnel into the bottom or side of a lava pool, you'll have a few moments to throw a block of dirt or stone into the gap to stem the flow, while with water it'll flood almost instantly. This also means that even once you get rid of a lava source block or block off the flow, the part that's cut off from the source block will take quite a while to disappear.