Final mask guardian

The Final mask guardian is an invisible creature guarding a hallway northeast of the Director, and east of another small chamber containing a Mask guardian.
==Gameplay==
The Final mask guardian occupies a hallway with an entrance door and a back door. The back door is initially sealed, and unable to be lockpicked or bashed. Examining this door will reveal an on-screen text message:
If a party member enters the hallway and is not wearing the Mask of King Strohm III, they will be struck by a Sunfire explosion every round. To reveal the source of the Sunfire spells, divination spells such as Invisibility Purge, Detect Invisibility, or True Sight can be used to make the Final mask guardian visible, however the Sunfire explosions will continue.
When an exploring party has someone wear the Mask of King Strohm III (equipped as a helmet), three things occur:
First, the party can see what appears to be a Fire Elemental within this chamber. Second, the Mask removes the invisible force preventing the door from being opened. Third, the worn Mask prevents the creature from being able to use the Sunfire ability.
Once the previously invisible creature is exposed, it will attack the closest party member it can detect using its melee attacks. The creature is 100% resistant to fire and magic, so physical attacks are recommended.
When the fiery guardian is put down, the party may advance to the King's burial chamber. In some rubble on the chamber floor will be Peridan and the Dragon Scale Shield - items which may be useful later in this dungeon. 
==Mod content==
The Sword Coast Stratagems mod makes minor revision to this creature, adding the usual SCS status effect immunities that a fire elemental has with that mod, such as protection from Panic, moral break, paralyze and that sort of thing. It alters nothing else.