Area Effect Clouds and Lingering Effects

Minecraft Bedrock includes the `minecraft:area_effect_cloud` entity out of the box, which handles lingering potions. However, its radius shrinking, potion color blending, and effect application are largely hardcoded in the game engine. You cannot easily spawn a vanilla area effect cloud via `/summon` and give it custom behavior through JSON without breaking normal lingering potions.

Because of this limitation, the standard practice for add-on creators is to build a bespoke dummy entity that mimics an area effect cloud. By combining a timer, a damage sensor, and a repeating behavior or animation, you can create poison gas traps, healing circles, radiation zones, or ground-targeted boss attacks without touching the vanilla potion system.

A proper effect cloud should not be pushable, attackable, or capable of blocking arrows and building placement. To achieve this, you strip away movement components, shrink or remove the collision box, and add a `minecraft:damage_sensor` that rejects all incoming damage.

You also need `minecraft:physics` configured so the cloud does not fall through the world if you want it to rest on the ground, or disable gravity entirely if you want it to float in mid-air where it was spawned. Adding the `minecraft:pushable` component with both flags set to false stops pistons and walking mobs from sliding the cloud out of position.

To apply status effects or damage to entities standing inside the cloud, the most reliable JSON-only approach is to combine `minecraft:area_attack` with a `minecraft:timer` that eventually cleans up the entity. `minecraft:area_attack` automatically damages anything within a specified range on a cooldown, and you can filter it so the boss or player who spawned the cloud is immune.

If you want to apply status effects like Poison, Wither, or Regeneration instead of raw damage, you pulse an event using `minecraft:timer` set to loop. Each time the timer fires, the triggered event runs `queue_command` to execute an `/effect` or `/damage` command targeting entities within a specific radius (`r=4`). When the cloud's lifetime is up, a second non-looping timer triggers `minecraft:instant_despawn` to remove the entity cleanly.

{
  "format_version": "1.20.80",
  "minecraft:entity": {
    "description": {
      "identifier": "wiki:poison_cloud",
      "is_spawnable": false,
      "is_summonable": true,
      "is_experimental": false
    },
    "component_groups": {
      "wiki:despawn_cloud": {
        "minecraft:instant_despawn": {}
      }
    },
    "components": {
      "minecraft:type_family": {
        "family": [ "inanimate", "cloud" ]
      },
      "minecraft:collision_box": {
        "width": 0.0,
        "height": 0.0
      },
      "minecraft:physics": {
        "has_gravity": false,
        "has_collision": false
      },
      "minecraft:pushable": {
        "is_pushable": false,
        "is_pushable_by_piston": false
      },
      "minecraft:damage_sensor": {
        "triggers": [
          {
            "cause": "all",
            "deals_damage": false
          }
        ]
      },
      "minecraft:area_attack": {
        "damage_range": 3.5,
        "damage_per_tick": 2,
        "damage_cooldown": 1.0,
        "cause": "magic",
        "entity_filter": {
          "all_of": [
            {
              "test": "is_family",
              "subject": "other",
              " operator": "not",
              "value": "monster"
            },
            {
              "test": "is_family",
              "subject": "other",
              "operator": "not",
              "value": "inanimate"
            }
          ]
        }
      },
      "minecraft:timer": {
        "looping": false,
        "time": 10.0,
        "time_down_event": {
          "event": "wiki:expire"
        }
      }
    },
    "events": {
      "wiki:expire": {
        "add": {
          "component_groups": [ "wiki:despawn_cloud" ]
        }
      }
    }
  }
}

Because a custom cloud entity has no physical body, you usually give it an empty or single-bone geometry and a completely transparent texture (or omit the render controller entirely so no mesh is drawn). The visual presence of the cloud comes entirely from a custom particle emitter attached to the entity's client definition.

In your resource pack entity file, link a particle effect and trigger it continuously using a client animation. A disc-shaped particle emitter works best for ground hazards. By driving the particle emission from a client animation set to loop in `scripts/animate`, the particles will play automatically for as long as the cloud entity exists in the world, and stop the moment `minecraft:instant_despawn` removes it.

{
  "format_version": "1.10.0",
  "minecraft:client_entity": {
    "description": {
      "identifier": "wiki:poison_cloud",
      "particle_effects": {
        "cloud_fumes": "wiki:poison_fumes_particle"
      },
      "animations": {
        "emit_particles": "animation.wiki.poison_cloud.emit"
      },
      "scripts": {
        "animate": [
          "emit_particles"
        ]
      }
    }
  }
}

Area effect clouds are rarely placed by hand; they are almost always spawned when a thrown potion, magic projectile, or boss attack hits the ground. On a custom projectile entity, you can use the `minecraft:projectile` component's `on_hit` trigger with the `spawn_chance` parameter to summon your `wiki:poison_cloud` right at the impact coordinates.

Alternatively, if a boss mob is creating a hazard zone around itself, you can use `minecraft:spawn_entity` inside a component group that only activates during the boss's special attack state, or run `/summon wiki:poison_cloud ~~~` via an animation controller or event response.

Applies to Bedrock Edition 1.16.0 and newer (example uses 1.20.80 format). No experimental toggles are required.

Read out of the game itself, so the ids match the version you are building for.