If event matching the room index is set, these enemies will not spawn upon entry.

Does not set events itself.

Best to use in conjunction with your pick of Event ASM and either my version or JAM'S version of the Event Gray Doors (otherwise you can be softlocked by leaving and reentering a room you cleared.)

Must set the Metroid Initial AI to $FA00 inside the Enemy DNA editor for this to take effect. (Vanilla location is $F330.)

Requires some setup, but will save a roomstate if all you want is a Metroid cleared room.

Credits to P.JBoy and MetroidNerd#9001.