Githyanki Knight

(from Planescape: A Guide to the Astral - 1996):

KNIGHTS

Knights are the greatest of the githwarriors, and therefore some of the most influential of the githyankl. These folks're warriors who have devoted themselves to the direct service af the lich-queen (before her reign, no githyanki knights existed). They serve as her eyes aid ears in all situations, so any important mission’ll have at least one knight, and all fortresses, towns, of outposts also have a knight. People both revere and fear the knights, for they know that they report directly to the queen. Failure in githyanki sociely is bad, but failure in front of a knight is usually a fatal mistake. 

Knights never become higb-ups in the conventional sense but are always involved in important decisions, and it is forbidden to keep secrets from them. Essentially, they function outside the normal hierarchy. In addition to serving as elite combat troops, knights monitor internal affairs and enforce the will of the queen and whatever supreme leader they are assigned to.

Knights are as close to religious figures as the githyanki have, since there are no priests or clerics of any kind. The githyanki are too centered around the concept of individuality to have a formal, organized religion, but since the coming of the lich-queen, their reverence for her approaches worship. They recognize no other gods. It is difficult for a people who build their homes on the backs of dead powers to recognize such beings to be divine.

As they focus so much devotion toward their mistress, the knights gain quasi-religious pawers. Each knight has the special abilities of a paladin, except that

they are perverted toward evil. These reversed abilities include detect good (as the spell) at will, cause disease (as the spell) once per week for every five levels, protection from good, 10' radius (continuous), and they can cause wounds

by their touch, inflicting 2 points of damage per experience level once per day. Like paladins, they’re immune 10 disease and gain a +2 bonus 10 all saving throws. Because the lich-queen's not an actual deity, they gain no power over undead and don’t receive any spells from her. The protection from good power is particularly useful against meddlesome primes or even invaders trom planes other than the Astral.

Knights carry the infamous silver swords known throughout the planes. These special magical two-handed blades can sever the silver cord of a sod traveling through the Astral in an astral form (see below). These weapons are given to knights of 7th level or higher. Half of those of 5th or 6th level wield two-handed swords +1, the rest using nonmagical two-handed swords. Those of lesser status use either long swords and shields or two-handed swords.

Knights always wear plate mail or plate armor — it doesn’t affect their movement on the Astral Plane at all. 

Some knights ride nightmares into battle, but only when the fiendish steeds' combat abilities are important, because the knights are faster unmounted.

(From 5th Edition Monster Manual - 2014):

The githyanki plunder countless worlds from the decks of their astral vessels and the backs of red dragons. Feathers, beads, gems, and precious metals decorate their armor and weapons—the legendary silver swords with which they cut through their foes. Since winning their freedom from the mind flayers, the githyanki have become ruthless conquerors under the rulership of their dread lich-queen, Vlaakith.

Astral Raiders. The githyanki despise all other races, undertaking devastating raids that take them from their strongholds in the Astral Plane to the far-flung corners of the multiverse. War is the ultimate expression of githyanki culture, and their pitiless black eyes know no mercy. After a raid, they leave shattered survivors enough food and resources to weakly endure. Later, the githyanki return to their conquered foes, plundering them again and again.

Followers of Gith. In their own language, githyanki means “followers of Gith.” Under the guidance of Gith, the githyanki stratified into a militaristic society, with a strict caste system, dedicated to the ongoing fight against the victims and sworn enemies of their race. When their leader Gith perished, she was replaced by her undead adviser, Vlaakith. The lich-queen forbade worship of all beings except herself.

Of all their enemies, the githyanki most hate their former masters, the mind flayers. Their close kin, the githzerai, are second in their enmity. All other creatures are treated with simple contempt by the githyanki, whose xenophobic pride defines their view of inferior races.

Silver Swords. In ancient times, gith knights created special weapons to combat their mind flayer masters. These silver swords channel the force of the wielder’s will, dealing psychic as well as physical damage. A githyanki can’t become a knight until it masters the singular discipline needed to will such a blade into existence. A silver sword is equivalent to a greatsword, and takes on the properties of a +3 greatsword in the hands of its creator.

In the eyes of the githyanki, each silver sword is a priceless relic and a work of art. Githyanki knights will hunt down and destroy any non-githyanki that dares to carry or wield a silver sword, reclaiming it for their people.

Red Dragon Riders. In the uprising against the illithids, Gith sought allies. Her adviser Vlaakith appealed to Tiamat, the goddess of evil dragonkind, and Gith ventured into the Nine Hells to meet with her. Only Tiamat now knows what passed between them, but Vlaakith returned to the Astral Plane with the Dragon Queen’s red dragon consort Ephelomon, who proclaimed that his kind would forever act as allies to the githyanki. Not all red dragons honor the alliance kindled so long ago, but most at least don’t consider the githyanki their enemies.

Outposts in the Mortal Realm. Since creatures that dwell on the Astral Plane don’t age, the githyanki establish creches in remote areas of the Material Plane to raise their young. Doubling as military academies, these creches train young githyanki to harness their psychic and combat abilities. When a githyanki grows to adulthood and slays a mind flayer as part of a sacred rite of passage, it is permitted to rejoin its people on the Astral Plane.