Giganto Weapon

Giganto Weapon is a type of Chimera. It was the fearsome biological relic used in wars a thousand years ago. It was so powerful that it was kept locked up at the Monster Lord's Castle. Like a normal chimera, it is emotionless and attacks as it pleases.

As Luka ventures through the Monster Lord's Castle, the Four Heavenly Knights observe his progress; Tamamo decides it's time to use "that" to amuse themselves. Continuing on, Luka senses a horrible presence. In the shadow lurks a lowly Imp; he speculates that she is not the cause of the presence, and then swats her aside. Just then, the abomination crashes through the roof. Tamamo appears briefly to explain the origin of the weapon, and disappears. Luka barely manages in the battle just as he finally whittles away all of the beast's health, however it begins to enter a regeneration state and heals. Salamander chimes in and tells him that he must damage her faster than she can regenerate, and teaches him Vaporizing Rebellion Sword. With that technique, the Giganto Weapon is sealed into what appears to be a lion. Conquering the beast, he thinks back on the Chimeras he fought earlier: why are they and the Giganto Weapon so similar?

Encyclopedia Entry
"An artificial monster created at the time of the Great Monster Wars. Containing the superior aspects of many different monsters, she's an incredibly powerful Chimeric monster. Discovered unmoving in an unused portion of the castle her creator is unknown. Using the knowledge remaining from the Great Monster Wars, she was able to be repaired to the point of being operational again. Despite that, she is still far weaker than she was during the Great Monster Wars.

''Though she follows the orders of the one she registers as her master, her destruction impulse is so strong she sometimes goes berserk. Binding any animal with her tail, she will mechanically squeeze out their semen to use as her power source. Of course, the most energy dense semen is found in human males."''

Battle Overview
As a biological relic from a thousand years prior to the game's events as well as a chimera, she should definitely not be underestimated. Giganto Weapon has many deadly attacks, so Gnome is necessary for this fight. Additionally, Disrupting Roar can put Luka in paralysis, so Sylph has her roles. Starting off the battle with the Undine + Serene Demon Sword combination can whittle some of her health away. Saving SP for summons and Meditation is strongly advised.

Aside from her high damage, her Semen Squeezing Program acts as a KO move; her tail expands, ready to grasp him. If Luka does not Guard, it will end him.

Once her health goes all the way down, she uses Regeneration and heals 3,000 HP. Salamander tells him that he must dish out more damage than she can heal, and teaches him Vaporizing Rebellion Sword. Using it, the Giganto Weapon falls. Using Salamander here can be quite helpful to restore SP if Luka does not have enough for Vaporizing Rebellion Sword, however this is a risky tactic as Luka becomes vulnerable. If Luka tries to defeat the Giganto Weapon without Vaporizing Rebellion Sword, the beast will heal again.

Overwhelmed by the beast, the tail grabs him as he is brought to the female body of the creature, being stimulated by the hole within the tail as the Giganto Weapon's tongue licks his, absorbing his energy from two different ends. With that, the beast emotionlessly extracts all his semen and discards the lifeless corpse.

Trivia

 * Giganto Weapon is the only chimera to be under control of the Four Heavenly Knights as opposed to Promestein.
 * Giganto Weapon is an obvious nod to Final Fantasy's Ultima Weapon, aside from the various visual similarities she is also a strong monster used as a weapon in an ancient war.
 * Much like the above-mentioned basis, she has her own battle theme.