"The Fiend of Fire, who uses the many limbs of her serpentine body to wield deadly weapons."
Marilith(マリリス,Maririsu?), also known as Kary (a mistranslation of Kali) or Marylis, is the Fiend of Fire from the original Final Fantasy. She appears in Mount Gulg as a woman with the lower body of a snake and has six arms, each wielding a sword.
After defeating the Fiend of Earth, Lich, the party travels by ship to Crescent Lake to find the famed Circle of Sages, led by the prophet Lukahn. One of the sages gives the Warriors of Light a canoe, so they may travel on rivers to reach the volcano Mount Gulg, where Marilith had lain dormant by the Fire Crystal until the Lich's demise disturbed her from slumber, two hundred years before she was due to awaken. At the bottom floor of the lava-ridden volcano, the Warriors of Light defeated the enraged Marilith in a fiery battle, allowing the Fire Crystal to glow once again.
Marilith's battle is not as difficult as Lich's, mainly because she is not stronger in comparison to the Warriors of Light's levels. It is recommended to start the battle with NulBlaze and Protect to be safe from her attacks. If the Flame Equipment (which can be found in a chest in the dungeon) has been obtained, the battle will be much easier. Contrary to popular belief, Marilith is resistant to Ice-based magic, so Blizzard may not be the best spell to cast.
Instead, use Silence to stop her use of spells and special abilities, then Slow to weaken her physical attacks. You can also Confuse her to have her waste turns or use Sleep. You can also buff physical attackers' strength with Temper and Haste. Keep in mind that she will always wake on her next turn but if you follow a battle pattern which you consider effective against her, then she will be no threat to you at all.
To truly exterminate the Fiends in the future and prevent them from sending Garland back to the past, the Warriors of Light had to kill the four Fiends before their pact with Garland was made. In the Chaos Shrine of the distant past, the second basement level, known as the "Kary Room", is full of monsters from Mount Gulug. Before heading down the stairs to the next floor, the party must best Marilith at her prime. Without the grog of interrupted sleep, the battle is harder than the last, but the same defensive (NulBlaze, Protera) and offensive (but not the Blizzaga spell) attacks will still smolder this Fiend's flaming anger.
Marilith's name and design were inspired by the Dungeons and Dragons Marilith, which is a demon in the form of a six-armed snake-tailed woman.
"Kary" was a mistranslation of the Hindu Goddess of Destruction Kali; the name change was probably an effort to avoid potential copyright issues with Dungeons and Dragons source material, similar to the changes made to the Beholder (Evil Eye).