Mythic figure, the defender of Nalos. Legend tells of the three armaments possessed by the Immortal Knight; the Immortal Helm, the Immortal Breastplate, and the Immortal Blade.

The Immortal Knight, the most famous hero in Nalos, charges forward under Queen Gimnax’s banner. He leads a troop of Halflings, Dwarves, and Elves. - Crack in Kulbak (RPA-ADV5) 

• The Immortal Knight is a title is passed down to multiple people over several generations.
• Sometimes called the Red Knight.
• Only one Immortal Knight is ever in existence at a time.
• A player can become the Immortal Knight in Roll Player Adventures (RPA-ADV10).
• The Immortal Knight has three unique armor/weapon pieces: Immortal Blade, Immortal Breastplate, and Immortal Helm.
• The known holders of this title are Imbri, Landrus, and Sir Faris, who is pictured on the cover of Roll Player.

Tarik Nowlin introduces himself as connected with the Immortal Knight;

“Tarik Nowlin, Special Operative of King Taron, Confidant of the Immortal Knight, and Bearer of Bad News and Terrible Secrets!” - Battle at Blacklake (RPA-ADV1)

The Orc Undercity Thieves Guild guard mentions in passing that during the Dragul Invasion the Immortal Knight fought alongside Tarik Nowlin in the Black Dunes, slaying a Dragon.

More history of the Immortal Knight is established visiting Azema's Bones;

It was then that she [Azema] forged the armaments of the Immortal Knight, defender of Nalos, who was the first being to cross into Ulos from another plane. - Outbreak in Undercity (RPA-ADV3)

You see the forces of Khathandor and those of the Immortal Knight about to clash on the battlefield in a dream your first night at Kulbak Prison:

• Aid the Dragul:
  • Succeed, and overcome the Immortal Knight.
  • Fail, and be taken away in chains.
• Rally behind Nalos:
  • Succeed, and overcome Khathandor.
  • Fail, and the Dragul emerge victorious.

The Immortal Blade, weapon of the Immortal Knight, is found in the King's Guard Camp in Bogroot Swamp;

Elsifor floats across the camp to a sword with a red metal hilt lodged firmly into a root stump…It is the sword of the Immortal Knight, a sacred treasure to Nalos and a fine blade, as well. - Bogroot Demon (RPA-ADV6)

You can attempt to help General Grik and his soldiers fight the ice wyrm on the site or move to claim the sword.

After the battle at Nebblis, Plane of Flame, King Taron comments on your wearing of the Immortal Helm;

“You handle yourself well in battle. We of Nalos are lucky to have you. Did Tarik tell you about the…” King Taron cuts himself short, pointing at the side of your helm. “….well, never mind,” he says. “You’ll discover its secrets soon enough, I’m sure.” - Gate of Brizoor Waal (RPA-ADVF)

Following the events at Brizoor Waal, a navigational system seems to have activated about the Immortal Helm;

Ever since the gate opened, the Immortal Helm has been acting strangely. It makes noises at times and projects odd images into your eye when you wear it. You guess these are maps, perhaps maps of the planes and their connections, but none of the paths it suggests leads to Brizoor Waal. Instead there are little shifting pockets of activity all over Nalos where a link might be made to some other place. When time and safety permit, you may explore one of these sites and see where it takes you. - Gate of Brizoor Waal (RPA-ADVF)

It is alluded that the Immortal Knight is not a single being but a mantle passed across multiple individuals when a projection from a control collar appears to malfunction:

Something seems to go wrong with the projected image of the Immortal Knight. At first it flickers in and out of existence, but then the Immortal Knight’s form appears to change. In rapid succession, he cycles through a variety of bodies: a female Orc, a male Elf, and many others. The only thing that remains constant is the bright red armor. - Deathmatch at the Colosseum of Ashes (RPA-SQ1)

The Kobold Armaund Ra also relays that the Dragul general Khathandor defeated the Immortal Knight in battle at the Colosseum of Ashes;

“The Immortal Knight was defeated in the Colosseum by my great ancestor, Khathandor…Khathandor was the greatest Kobold warrior to ever live. No Human was ever his equal.” - Armaund Ra, Deathmatch at the Colosseum of Ashes (RPA-SQ1)

See Imbri.

When she broke the veil and forged our world
Azema’s flame lit torches three
The crimson blade and plate and helm
To warm our hearts immortally
These three were claimed by one so brave
To climb the pyre of her bones
And pledge forever after that
Allegiance to the crown of Nalos
Oh Nalos, oh Nalos
Is her flame still burning bright
In the helm and plate and blade
Of your immortal knight

By Tarik Nowlin

Earning the rank of champion, the Immortal Knight was offered his freedom by the Grandmaster of Games. Refusing, he demanded liberty for all combatants. Amused by this request, the Grandmaster agreed to release one gladiator of the Immortal Knight's choosing. It was through this means that King Taron was freed. After many more years in the colosseum, the Immortal Knight followed his lord back to Ulos. He found, to his dismay, that King Taron had built an arena of his own, subjecting combatants to the same cruelty he had witnessed in the Colosseum of Ashes.