From 1d4chan
The original picture, right out of Polyhedron
4e's version, now more visibly hybridized.

Duthka'gith are a mutant offshoot of the githyanki race from Dungeons & Dragons; distinguished by their bloodline having been tainted with both fiendish and red dragon influences, the duthka'gith were bred by Vlaakith CLVII as a race of super-soldiers to bolster the might of the githyanki people. Introduced in 3rd edition in the Incursion adventure path, with statistics for both generic duthka'gith NPCs and duthka'gith PCs appearing in Polyhedron #159, they later returned for 4th edition in "Secrets of the Astral Sea".

Duthka'gith literally trace their lineage to Ephelomon, the fiendish red dragon consort of Tiamat who first established the pact with Gith eons ago. Technically, this would just make them Githyanki with both the Half-Dragon (Red) and Fiendish Templates, but their unique origins make them creatures of a slightly different nature. The first duthka'giths were born of magical rituals in which fertilized githyanki eggs were somehow mutated through exposure to Ephelomon's "seed" - we don't know the details and frankly you're better off not thinking about them - but they've become a true-breeding race of their own since then.

The infusion of red dragon blood, with just a pinch of fiend ichors, means that duthka'gith are stronger, faster, tougher and smarter than their githyanki ancestors - worse still, they know it. These creatures combine the githyanki's propensity for cruelty and love of violence with all the arrogance of dragons, made worse by the toxic, resentment-fueled pressure cooker of githyanki society. Seeing themselves as favored by virtue of their birth, duthka'gith are notably boorish and savage, lacking all of the politeness and restraint that characterizes githyanki interactions with each other; duthka'giths see themselves as above the normal niceties of their ancestors' culture. Bred to lead, draconic arrogance means that duthka'gith quickly grow frustrated when forced to accept a lesser position of any kind.

This arrogance is so pronounced that they have even developed their own take on the githyanki faith in "Gith the Messiah"; according to this "duthka'gith heresy", Gith has been spent the eons partnered with Tiamat, and this has transformed her into a mighty hybrid of githyanki and red dragon - much like the duthka'gith themselves. As such, the birth of their species is a sign that she will soon return to walk amongst her people again, and lead them to victory in the Eternal Crusade.

As you might tell, relationships between duthka'gith and githyanki are strained at best. It doesn't help that many githyanki see them as inherently abominable for their mixed blood, and the creation of the duthka'giths is one of the things that has sparked some discontent with Vlaakith CLVII.

Still, even with this and their naturally chaotic tendencies, duthka'gith are a success story; they are naturally charismatic and intelligent, making them born leaders. And they're also lethally destructive. Truly, they combine the best - and the worst - of githyanki, red dragons, and fiends.

You're probably wondering at this point what that tainted ancestry actually does to the duthka'gith appearance. Well... surprisingly little, in fact. In 3.5, duthka'giths appear as... bigger githyanki (averaging close to 7ft tall and over 210 pounds) with red, scaly skin, untameably wild hair, bigger ears, and red-gleaming black eyes. Pretty disappointing, right? 4th edition made them slightly more half-dragon looking, with their sole picture depicting a githyanki with red scaly patches, dragon-like horns, and taloned hands reminiscent of dragon claws.

Statistics-wise, duthka'gith had the following statblock in 3.5:

+8 Str, +2 Dex, +4 Con, +2 Int, -2 Wis, +2 Cha
Base Speed 30 feet
Darkvision 60 feet
Low-light Vision
Psionics: At 1st level, can use the spell-like abilities of Daze Humanoid and Mage Hand 3/day each. At 3rd level, gain Blur (3/day). At 6th level, gain Dimension Door (3/day). At 9th level, gain Telekinesis (3/day) and Plane Shift (1/day).
Spell Resistance: 5 + 1 per total character level, maxing at SR 25 at 20th level.
Dragon Type
Breath Weapon (Su): 1/day, spit a 30ft cone of fire that deals 6d8 fire damage (half on a successful Reflex save of DC 10 + duthka'gith's Con modifier).
Natural Weapons: One Bite attack (1d6 + 1/2 duthka'gith's Str modifier), two Claw attacks (1d4 + duthka'gith's Str modifier).
Natural Armor Bonus: +4
Smite Good (Su): 1/day, inflict bonus damage equal to character level against a good opponent.
Energy Resistance: Immune to Fire, Cold Resistance 5
Githyanki Blood: A duthka'gith is considered to be a Githyanki for all special abilities, effects and requirements tied to race.
Level Adjustment: +5
Favored Class: Fighter

This statblock is clearly derived from the non-psionic githyanki in the same magazine; if one wanted to make them psionic as well, one would just replace Psionics and Spell Resistance with the Naturally Psionic, Psi-Like Abilities and Power Resistance trait from the Expanded Psionics Handbook's version of the githyanki.

The Gith of Dungeons & Dragons
Races: Duthka'gith - Gith - Githyanki - Githzerai - Half-Githzerai
Undead: Kr'y'izoth - Tl'a'ikith
Individuals: Vlaakith CLVII - Zaerith Menyar-Ag-Gith - Zerthimon
Places: Shra'kt'lor - Tu'narath
NPC Classes: Mlar
Prestige Classes: Blackweave Warlock - Ghustil - Gish Mindslayer - Holocaust Warrior - Sword Stalker
Adventures: Incursion - Scales of War
Miscellaneous: Crown of Corruption - Gish - Scepter of Ephelomon