The Guardian is a hostile mob that can only spawn underwater inside of or around ocean monuments. Its eye will always look toward a nearby player or a squid. There is a mini-boss variant called the elder guardian.
The guardian attacks by sending out a large laser beam which will kill a player. In addition, guardians can target and damage players who are riding in boats. However, once a player is out of range, the guardian's laser will disengage from a player, and it will deal no damage. The laser will also disengage if there is a solid block between the player and guardian, or if the player uses a shield. Guardians will swim around in water, and they will attack any players, squids, or dolphins that come into sight. They swim in abrupt charges and move their tail rapidly when doing so. Unlike squids, guardians will not die outside of water. Instead, they will jump and flail around while making wet and squishy sounding noises. They will also quickly move towards the nearest water source at which point they swim away. When they are swimming, their spikes will retract, and they won't deal any damage when attacked. When they are not swimming, they will sink. Guardians' eyes will follow and stare at any nearby players, and it will always look directly at who they're attacking. This makes them the first mob with dynamic eyes. As of 1.13, Guardians also attack fish mobs.
Guardians are very resistant to melee attacks when they are underwater since a player will not be able to quickly approach a guardian due to the water's slowing effect. Guardians will swim away when they are approached by a player it is targeting, and it will deal one of damage every time it is hit when its spikes are extended. If the guardian is cornered, it will often extend its spikes and simply fire at a player. Guardians are resistant to fire damage, but if they are somehow brought onto land they can take fall damage from their swift movement sometimes. If a player must fight a guardian in melee, they should either try to corner it and hope for the best or try to trick it into swimming within melee range repeatedly. If the guardian is in shallow water, a player(s) can use a fishing rod to pull it out of the water, so a player(s) can then kill it using melee attacks without being shot at or hurt by the spikes. Fighting guardians is incredibly dangerous without armor. Armor is essential when fighting guardians especially within the ocean monuments. Entering their territory without armor on will almost always lead to a swift death even if one is armed with a sword.
- The guardian's dynamic eye is actually part of the guardian's head for its model.
- Armor does not reduce the laser beams as much as it does other attacks: on hard the base damage is 9 HP hearts, and it ought to go down to 2 HP with full diamond armor, but instead it drops only to 5 HP.
- The guardian's laser sound can be heard up to 100 blocks away.
- Guardians can take fall damage, but it will take 34 blocks in order for them to fall to their death.
- Guardians were immune to fire damage from magma blocks until version 1.15.