12

A well-executed lateral mid-air morph can get into the passage without taking a hit. Otherwise, the Boyon can be used to push Samus into the passage.

Requires:

"canLateralMidAirMorph"
{
  "or": [
    "canTrickyJump",
    {
      "and": [
        "canNeutralDamageBoost",
        {
          "enemyDamage": {
            "enemy": "Boyon",
            "type": "contact",
            "hits": 1
          }
        }
      ]
    }
  ]
}
{
  "heatFrames": 350
}

Dev note: It's possible to get into the passage by a non-mockball mid-air morph, it just needs to be fairly late. Due to its risk and not really being easier, it's not included here