Minecraft wiki entry for Trap_design, associated text: Lava is a dangerous fluid to use. Any mob caught in lava will take periodic damage from it as well as periodic fire damage. Since lava spreads slowly the lava source should be close to the target, so it doesn't have much time to attempt an escape. Lava will destroy any item that falls in it. It can be used effectively in an enclosed space and triggered by a ceiling floodgate. Alternatively, a hole filled with lava that the target is pushed into doesn't require time for the lava to spread. It is also advisable to line such a hole with a block such as a furnace, so that the victim cannot place blocks to escape.