A guardian is presented as a pufferfish-like hostile mob that spawns in and around ocean monuments. Guardians can spawn only if the spawning block and the block below the spawning block are water. They swim around in the water, attacking players, dolphins, squid, axolotl, or glow squid that come into their range. A prismarine shard is an item, you can obtain by defeating guardians or elder guardians. You can use it to craft various prismarine blocks as well as sea lanterns. Minecraft Guardian and Prismarine Shard as a game cursor.