Minecraft wiki entry for Acquiring_a_conduit, associated text: Prismarine can be obtained from the guardians themselves and from the structure of the monument. The guardians can be a nuisance and the mining fatigue from elder guardians can make mining impossible. For these purposes, it is best to bring building materials that can be broken instantly such as slime blocks, scaffolding, or TNT. Killing guardians is much easier if the player has a trident enchanted with Impaling and Loyalty. A Riptide-enchanted trident or Depth Strider-enchanted boots are also helpful.