Galamoth is a giant dragon-like demon and a boss in Castlevania: Symphony of the Night, based on the non-canon spin-off games Kid Dracula. Galamoth has since then been referred in some games, but never appears in person. He wants to kill Count Dracula and take his place as the King of the Night.
In these games, Galamoth is called King Garamoth and goes by the title of the Space Emperor, hinting an extraterrestrial origin. He serves as the main villain and final boss. After an accidental slumber of 10,000 years, Dracula's son Kid Dracula (hinted to be Alucard, Dracula's son in the mainstream games) discovers that his father's place has been taken over by Galamoth, whom he resolves to defeat.
In this game, Galamoth appears as a huge, winged, humanoid dragon, depicted in a cartoon like way just like every other character. Kid Dracula first has to defeat Mecha Galamoth, a robotic double of the villain who fights with a lightsabre-like staff, with which he strikes and fires enormous energy beams. The real Galamoth flies all over the screen and mostly attacks by hurling lightning bolts towards the ground.
Castlevania: Symphony of the Night
Galamoth is fought as a Super-Boss of some sorts in Castlevania: Symphony of the Night. He is by far the most powerful and hardest to defeat of all the bosses in the game, but he has little to no importance in the plot and the game can be finished without challenging him. The entry about him states that he plans to rule the Netherworld and it is somehow implied that he is attempting to invade the Castlevania in order to take Dracula's throne. He is found late in the game in the Floating Catacombs, an area of the Reverse Castle which can be accessed after defeating Death and is filled with Frozen Halves. (Transexual ice-mages at Galamoth's command who can conjure a dangerous rain of giant blocks of ice.)
Galamoth is extremely hard to defeat. He is so big that he does not entirely fit onscreen and he mostly attacks with a magical staff that enables him to cast lightning spells. He is at level 50 and has an insane amount of life-points. It is highly advised to have Alucard at a similar, if not higher, level than his own and to equip him with Lightning-resisting armour, as well as lots of potions, healing items and Resist Thunder items to stand a chance against him.
He is very, very resilient and uses devastating attacks: he kicks forwards or backwards whenever Alucard comes too close to him, he smashes his staff on the ground to crush Alucard, he raises his staff over Alucard and conjures a long-lasting onslaught of lightning, he raises his staff and conjures a rain of giant spheres of darkness and lightning, and he fires a large electric arc in front of him whenever Alucard stands on the platforms at eye-level. The ability to turn into mist for as long as necessary is very useful to dodge his attacks.
Alucard must strike Galamoth in the head to deal bigger damage, but considering how tall the demon is, this is easier said than done. Alucard must jump on the platforms on the room's walls and unleash as many long-range attacks and special projectiles as he can, while dodging the demon's electric arcs, but after a short while, Galamoth steps backwards and exits the screen out of reach. It must be noted that punching Galamoth's face stuns him for a short while, meaning that he can be defeated by spamming punches over and over so that he cannot exit the screen. However, punches deal very little damage, meaning that defeating this way is horribly long, and unlikely to last the entire fight.
Galamoth acts as the primary antagonist by proxy in the fighting game Castlevania Judgment. He is never mentioned by name but he is heavily implied to be the master of the Time Reaper. the game's final boss who was sent from 10,000 years in the future to kill Dracula, so that his lord could become the King of the Night. (Galamoth's name can be heard in the Time Reaper's screams of defeat; and 10,000 years in the future being an obvious nod to the Kid Dracula game.) However, the Time Reaper is sealed in a Time Rift by the mysterious Time Master Aeon and killed by the game's characters.
Castlevania: Aria of Sorrow
It is implied in the game Castlevania: Aria of Sorrow that Dracula settled his score with Galamoth and killed him, some times before being slain once and for all in 1999. Indeed, Galamoth's soul can be found by the primary protagonist Soma Cruz (who is Dracula's reincarnation and is able to absorb the souls and powers of fallen monsters). The soul is found by breaking one of the Castlevania's candle, who have been stated to contain the souls of Dracula's victims.
Galamoth's soul is mandatory to win the game, as the power it grants is the only way to bypass the time freezing abilities of the Chronomage monster.