Terasology is described as '(started under the name Blockmania) is an open source project started by Benjamin “begla” Glatzel to research procedural terrain generation and efficient rendering techniques in Java using the LWJGL' and is a Sandbox Game in the games category. There are more than 50 games similar to Terasology for a variety of platforms, including Windows, Mac, Linux, Android and iPhone apps. The best Terasology alternative is Minecraft. It's not free, so if you're looking for a free alternative, you could try Luanti (formerly Minetest) or Veloren. Other Terasology like games are Roblox, VoxeLibre (formerly MineClone2), LEGO Worlds and Vintage Story.