Obsidian

Obsidian is a block found naturally in all dimensions, and created when water flows over a lava source in the Overworld, or as part of structures in the Nether and the End. It has high hardness and blast resistance, making it immune to normal explosions. Obsidian can be used to craft beacons, enchanting tables, and ender chests, and build the frame of a Nether portal. Obsidian is only obtainable with a diamond or netherite pickaxe.