Minecraft wiki entry for Multiplayer_PvP_bases, associated text: If you do decide to build a base inside a monument, it is advised to place a massive roof (60x60) above the entire area (Preferably made of glass, and at block limit level 256 so to be less noticeable), so that the guardians spawn more often to defend you. Flooding any nearby caves in at least a 100x100 area will also help this.