Serpci

Serpci is the eleventh boss encountered in Luigi's Mansion 3, who haunts the Tomb Suites and guards the eleventh floor elevator button.

Appearance
Luigi first finds her by opening her sarcophagus in her room, which awakens her. She then activates a trap that sends Luigi down to a sandpit maze, to which he must make his way back up to the main room.

Luigi stumbled upon her room again by accident after mimicking a pose in his likeness engraved on the wall. She then laughs before leaving the room.

After he enters the desert area, she then pranks him by "blowing him a kiss" from behind and spraying sand on him, before forming a sand tornado to create a sand mound in the likeness of her face.

Battle
She will largely be contained in the sand mound, and will attack by pounding in a blob of sand or otherwise using sand cobras from the mound, appearing quickly to taunt the player.

To beat her, first the player needs to suck in as much sand from the mound as possible to cause it to collapse, then she'll expose herself with six cobras, and then launch them, giving an opening to flash her and suck her in. Upon being defeated, she'll adopt a resting pose as she's sucked in, also supplying Luigi with the eleventh floor button.