Minecraft wiki entry for Adventure_survival, associated text: Accessing the nether in adventure mode is really hard but possible. To build the nether portal you need to find a 5 blocks deep lava pool and to use creepers to funnel water so that it converts the bottom-most layer of lava into obsidian. Then, using the endermen's ability to place blocks, you need to remove all the lava sources except those which will create the portal. Endermen however will only place blocks where there is air, meaning that you will need a platform over the lava pool where endermen could place gravity affected blocks, then a creeper to blow up the platform to make those blocks fall into the lava and remove the lava sources you don't need. You can then funnel more water to convert the remaining lava into obsidian, remove the water you used with the endermen's help once more and remove the blocks you used to remove the lava by exploding a creeper.