Greatswords in Elden Ring: Nightreign are heavy weapons that combine decent damage output, strong poise breaking and staggering capabilities with versatile movesets. Known for their wide sweeps and thrusts, they can stagger most enemies and are highly effective against almost any enemy. Though slower than lighter blades, their balance of power and reach makes them a staple for a lot of Nightreign builds.
NightreignGreatswords - Nightreign Wiki

Alabaster Lord's Sword
Greatsword • Lvl Required 7
Weapon Skill: Alabaster Lord's Pull
Thrust the armament into the ground to create a gravity well. In addition to dealing damage, this attack pulls enemies in. Has a greater area of effect than Gravitas.
Greatsword forged from a blue-white meteoric ore. The blade conceals gravity-manipulating magic. A weapon unique to the Alabaster Lords, a race of ancients with skin of stone who were said to have risen to life when a meteor struck long ago.

Banished Knight's Greatsword
Greatsword • 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.
A finely-crafted greatsword intricately engraved with an ancient motif. Given to knights who, whether by misfortune or misdeed, were forced to abandon their homes. Most of these knights were sent to the fringes, where they were forced to start anew with only despair for company.

Bastard Sword
Greatsword • 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 large sword with a straight blade. This heavy sword is usually wieldedwith two hands, but for those with enough strength, one is sufficient. The hefty blade can be swung into multiple foes at once thanks to the broad, sweeping attack, making fending off crowds all the easier.

Blasphemous Blade
Greatsword • Lvl Required 10
Weapon Skill: Taker's Flames
Raise the sacred sword aloft to set it ablaze with blasphemous flames, then bring it down to fire off a forward blast. The flames steal HP from those they touch.
Unique Weapon Passive: Power of the Blasphemous
Sacred sword of Rykard, Lord of Blasphemy. Remains of the countless heroes he has devoured writhe upon the surface of this blade. Now they share the same blood, bound together as family.

Claymore
Greatsword • Lvl Required 3
Weapon Skill: Lion's Claw
Skill of the Redmanes, who fought alongside the General Radahn. Somersault forwards, striking foes with armament.
A large sword with a long, straight blade. This heavy sword is usually wielded with two hands, but for those with enough strength, one is sufficient. In addition to the heavy sweeping attacks, it can also make a heavy piercing thrust making this a versatile weapon.

Dark Moon Greatsword
Greatsword • Lvl Required 10
Weapon Skill: Moonlight Greatsword
Raise the sword aloft, bathing it in the light of the dark moon. Temporarily increases magic attack power and imbues blade with frost. Charged attacks release blasts of moonlight.
Unique Weapon Passive: Power of Dark Moon
A Moon Greatsword, bestowed by a Carian queen upon her spouse to honor long-standing tradition. One of the legendary armaments. Ranni's sigil is a full moon, cold and leaden, and this sword is but a beam of its light.

Death's Poker
Greatsword • Lvl Required 7
Weapon Skill: Ghostflame Ignition
Thrust out the barbed rod and set its tip alight with ghostflame. Follow up with a normal attack to set the ground ablaze with ghostflame, or a strong attack to trigger a massive explosion.
Barbed rod carried by Deathbirds. The birds are graveyard fire keepers; it is said they rake out the ashen remains of the dead from their kilns.

Flamberge
Greatsword • 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.
Greatsword featuring a flame-like undulation. Shreds enemy flesh, inducing blood loss. Scarlet rot is kept at bay with flame at Redmane Castle, and as such, this beloved sword of Jerren's eventually became the symbol of the castle itself.

Forked Greatsword
Greatsword • 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.
Oddly shaped greatsword wielded by imps. The gently undulating forked blade is known as an "imp's tongue" and causes blood loss.

Gargoyle's Blackblade
Greatsword • Lvl Required 7
Weapon Skill: Corpse Wax Cutter
Lost skill of ancient heroes. Lift the sword up high to release the power of corpse wax and launch it forwards as a blade-like projectile.
Bronze greatsword wielded by Valiant Gargoyles mended with blackened corpse wax. Deals holy damage. Such is the mark of those who serve Maliketh, the Black Blade.

Gargoyle's Greatsword
Greatsword • Lvl Required 3
Weapon Skill: Vacuum Slice
Lost skill of ancient heroes. Hold the armament aloft to surround it with a shearin vacuum, then launch it forwards as a blade-like projectile.
Bronze greatsword wielded by Valiant Gargoyles. Just like the wielder, the missing parts have been mended with corpse wax; a patchwork of champions.

Golden Order Greatsword
Greatsword • Lvl Required 10
Weapon Skill: Establish Order
Raise the armament in a salute, releasing a golden explosion. Repeated inputs send out waves of golden light.
Unique Weapon Passive: Power of the Golden Order
Greatsword made of light, modeled after the Elden Ring itself. Forged by King Consort Radagon to proudly symbolize the tenets of the Golden Order. One of the legendary armaments. Telltale signs betray that this was once the greatsword bequeathed to him by his first wife, Rennala.