Culex is an optional boss in Super Mario RPG: Legend of the Seven Stars. He is the hardest boss in the game, even harder than the final boss, Smithy. Square, who worked with Nintendo on this game, created Culex as a homage to Final Fantasy.
Culex is the Dark Knight of Vanda, and was sent to the Mario universe by the Dark Mage, presumably to conquer the kingdom.
The way to get to Culex, as well as fighting him, is completely optional and none of it needs to be completed in order to beat the game. In Monstro Town, a Piranha Plant told Mario that the occupant of the next room was talking about evil and crystals. One of the doors - the door beside the room the Piranha Plant was in - was sealed shut by a mysterious force. In Moleville, Mario bought fireworks off one of the moles and sold it to a young mole girl for the Shiny Stone. Mario used the Shiny Stone to open the sealed door and enter a dimensional rift, where he met Culex. Culex told Mario who he was and that the Dark Mage sent him, but this world is uninhabitable for him so he must return to his universe. But first, he asked to challenge the world's strongest knight, which was Mario. Mario, Mallow, Geno, Bowser, and Princess Peach fought Culex and defeated him. Culex gave Mario a Quartz Charm to remember the battle, and returned to his dimension.
It is unclear whether Culex is evil or not; though he is a dark knight and works for a dark mage, and may have been sent to conquer the Mushroom Kingdom, he shows great respect toward Mario when Mario defeats him. He does say "Perhaps in another time, another game, we may have been mortal enemies. Let us part as comrades in arms." The "another game" part of this line is breaking the fourth wall.
Culex has 4096 HP. Though this is less than that of the final boss, he has four Elemental Crystals with him as his partners, which have their own powerful attacks. Culex himself uses Flame Stone, Meteor Blast, and Dark Star. He also does a standard physical attack for massive damage, and there is very little warning to this (similar to Bundt), as, being a Final Fantasy type character, his sprite stays in the same position. He also uses Shredder often. His attack power is 250, defense is 100, magic attack is 100, and his magic defense is 80. His attack power is the only stat to exceed that of Smithy; his defense and magic defense are lower while his magic attack is the same.
The Fire Crystal has 2500 HP. It uses fire based attacks, as its name implies. The Water Crystal has 1800 HP, but uses ice attacks. The Earth Crystal has 3200 HP, but less defense and attack power than the Fire and Water crystals (though its Blast, Boulder, and Storm attacks are capable of inflicting heavy damage), and uses earth and water attacks. The Wind Crystal has 800 HP but has sickening defense making it the hardest to destroy, however, its attacks hardly do any damage, although it does on occasion use Light Beam and Petal Blast, which put the victim to sleep and turn them into a mushroom, respectively. Despite its name, it uses electric attacks.
His Psychopath thought is "A little off, eh?"
- Similar to how his character design is based off of that of Final Fantasy, his battle theme is a Final Fantasy battle theme as well, as is the victory theme that plays when he is defeated.
- His HP, at 4096, is the square of 64, a significant and often used Nintendo number.