[
  {
    "type": "mapgen",
    "nested_mapgen_id": "portal_location",
    "object": {
      "mapgensize": [ 3, 3 ],
      "flags": [ "ERASE_ALL_BEFORE_PLACING_TERRAIN" ],
      "terrain": { " ": "t_region_groundcover" },
      "furniture": { " ": "f_rubble_rock" },
      "place_traps": [ { "trap": "tr_portal", "x": 1, "y": 1 } ]
    }
  },
  {
    "type": "mapgen",
    "update_mapgen_id": "mx_portal",
    "object": {
      "place_nested": [ { "chunks": [ "portal_location" ], "x": [ 2, 20 ], "y": [ 2, 20 ] } ],
      "monsters": { " ": { "monster": "GROUP_NETHER_PORTAL", "chance": 1, "density": 0.0001 } }
    }
  }
]
