Colossal Swords in Elden Ring: Nightreign are massive weapons that sacrifice speed for high damage output, as well as immence staggering power and poise breaking capabilities. While being a powerful type of weapon, their slow moveset requires players to commit to swings, which can leave you vulnurable to incomming attacks. These weapons are usually perfect for builds that focus around high damage and enemy stagger.
NightreignColossal Swords - Nightreign Wiki

Godslayer's Greatsword
Colossal Sword • Lvl Required 7
Weapon Skill: The Queen's Black Flame
Set the blade ablaze with the god-slaying black flame before delivering a sweeping slash. Additional input allows for a follow-up attack. The black flames will continue to wear down HP for a while.
Sacred sword of the Gloam-Eyed Queen who controlled the Godskin Apostles before her defeat at the hands of Maliketh. The black flames wielded by the apostles are channeled from this sword.

Grafted Blade Greatsword
Colossal Sword • Lvl Required 10
Weapon Skill: Oath Of Vengeance
Swear an oath upon the greatsword to avenge the clan, temporarily raising all attributes for a certain duration. While the oath's effects are active, poise will also be increased.
Unique Weapon Passive: Power of Vengeance
The storied sword of Castle Morne. A revenger's weapon, it is burdened with oceans of anger and regret. One of the legendary armaments. A lone surviving champion from a country now vanished was so determined to continue fighting that he claimed the swords of an entire clan of warriors.

Greatsword
Colossal Sword • Lvl Required 1
Weapon Skill: Stamp (upward Cut)
Brace armament and step into a low stance that prevents recoil from most enemy attacks. Follow up with a strong attack for an upward strike.
A coarse iron lump of an ultra greatsword. Mows down foes by utilizing its incredible weight. Though handling it likely requires the wielder to have surpassed the realm of the merely human, it is precisely for this reason the weapon is used to slaughter even inhuman foes.

Maliketh's Black Blade
Colossal Sword • Lvl Required 10
Weapon Skill: Destined Death
Set free the remnants of Destined Death, plunging the greatsword into the ground to summon a myriad of blades. In addition to dealing immediate damage, this attack reduces the enemy's maximum HP and continues to wear down HP for a short time.
Unique Weapon Passive: Power of Destined Death
Maliketh's black blade which once harbored the power of the Rune of Death. A sad shadow of its former glory. After a fragment of Death was stolen on that fateful night, Maliketh bound the blade within his own flesh, such that none might ever rob Death again.

Royal Greatsword
Colossal Sword • Lvl Required 7
Weapon Skill: Wolf's Assault
Infuse the greatsword with frost, then perform a forward somersault to plunge it into the ground. Then, pull it out to release a cold blast.
Greatsword decorated in royal Carian Style. Favored weapon of Blaidd the Half-Wolf. In defiance of the fate he was born to, Blaidd swore to serve no master but Ranni. As proof the sword was imbued with a cold magic at the moment oath was sworn.

Ruins Greatsword
Colossal Sword • Lvl Required 10
Weapon Skill: Wave Of Destruction
Raise the sword up high, then strike it against the ground to fire off a wave of gravitational force.
Unique Weapon Passive: Power of Destruction
Originally rubble from a ruin which fell from the sky, this surviving fragment was honed into a weapon. One of the legendary armaments. The ruin it came from crumbled when struck by a meteorite, as such this weapon harbors its destructive power.

Starscourge Greatsword
Colossal Sword • Lvl Required 10
Weapon Skill: Starcaller Cry
Bring the two swords together and roar into the skies, pulling in enemies with a gravitational wave. Follow up with an additional input to slam down with gravity-infused swords.
Unique Weapon Passive: Power of the Starscourge
Curved greatswords of black steel wielded by General Radahn. A pair of weapons decorated with a lion mane motif. Radahn earned considerable renown as the Starscourge in his youth, and it is said that it was during this time he engraved the gravity crest upon these blades.

Troll Knight's Sword
Colossal Sword • Lvl Required 3
Weapon Skill: Troll's Roar
Look into the distance and let out an intense roar, generating a powerful shockwave that blows back surrounding foes. Follow up with a strong attack to slam the armament down.
Greatsword embedded with a blue glintstone. Weapon of the trolls in service to the royal family of Caria. Called into service when the Queen invoked an oath they swore, the trolls are treated as true knights of Caria, and fight arm in arm with their human comrades.

Troll's Golden Sword
Colossal Sword • Lvl Required 3
Weapon Skill: Troll's Roar
Look into the distance and let out an intense roar, generating a powerful shockwave that blows back surrounding foes. Follow up with a strong attack to slam the armament down.
Sword given to the lesser giants who fought for the Erdtree during the War against the Giants long ago. Though the giants have lost their minds, they stay inseparable from their swords that are in sad shape—such that the gold plating had flaked away.

Watchdog's Greatsword
Colossal Sword • Lvl Required 3
Weapon Skill: Stamp (upward Cut)
Brace armament and step into a low stance that prevents recoil from most enemy attacks. Follow up with a strong attack for an upward strike.
Stone greatsword wielded by Erdtree Burial Watchdogs. Though decorated with the watchman's eye, the pupil was taken by graverobbers and is now hollow, leaving this sword a mere lump of stone.

Zweihander
Colossal Sword • Lvl Required 1
Weapon Skill: Stamp (upward Cut)
Brace armament and step into a low stance that prevents recoil from most enemy attacks. Follow up with a strong attack for an upward strike.
Just about the largest sword a mere man is capable of swinging. True to its name, it is designed to be wielded in both hands, but those of merely ordinary strength will still struggle to do so. The long blade is heavy and sharp, sending foes reeling back with its broader strokes, while also capable of a devastating piercing thrust.