Zaerith Menyar-Ag-Gith

Zaerith Menyar-Ag-Gith, also known as the Great Githzerai, is an obscure character from the Planescape campaign setting of Dungeons & Dragons. A powerful githzerai Fighter/Wizard (19th level and 23rd level, respectively), he is also known as the Wizard-King and the God-King, for he rules over the githzerai as an immortal master who is revered like a god, in a mirror-image of Vlaakith CLVII, from his throne in the great city of Shra'kt'lor.

Despite this auspicious status, Zaerith is actually a true non-entity in Planescape lore - maybe because the writers realized how hokey it was to give the githyanki and the githzerai mirrored rulers. First introduced in the Manual of the Planes for 1st edition AD&D, he was later covered in slightly more detail in The Book of Chaos, a component of the Planes of Chaos boxset. He was actually stated to exist in the githzerai's Monstrous Compendium entry, but he was deliberately left nameless - likewise, when 3rd edition's version of the Manual of the Planes was published, he was mentioned in passing in the single paragraph dedicated to Shra'kt'lor, but only as "The Great Githzerai".

According to the Book of Chaos, Zaerith rules Shra'kt'lor with the aid of ambitious generals, who think they are secretly usurping control from their God-King but are actually being manipulated by Zaerith, who takes great amusement from their "secret" plots and ploys. Like Vlaakith CLVII, he fears the potential of being overthrown by a strong githzerai mage, and so he forbids any who live in Shra'kt'lor from reaching higher than 9th level; on the rare occasions he needs the assistance of a more skilled githzerai mage, he takes them as an apprentice and trains them up, and then kills them when he doesn't need them anymore. However, he hasn't indoctrinated the githzerai to the same extent that Vlaakith has done with the githyanki, and so he hides this fact from his followers, less they follow their natural anarchistic inclinations and rise up to overthrow the tyrant they had once dared to trust.

For obvious reasons, Zaerith was never really that popular, and is slowly being pushed out of the limelight over the editions in favor of Zerthimon.

He has returned as of 5e. But as a very different character.

Rather than a lame, diet version of Vlaakith, Menyar-Ag (while his name hasn't actually changed, the book prefers to call him by the second half of his title, perhaps to distance his modern incarnation from his previous one) is, while still the immortal supreme ruler of the githzerai, something very...

Look, let's cast our mind back to previous editions. Let's say you really want to fucking min-max. So, you dump your physical stats all the way down to, like, three, or something, and put all the other points into your mental stats, then, you take the maximum possible aging penalties/bonuses. That's Menyar-Ag: someone who's physical body is in such aged, decrepit shape that he usually can't pass the physical tests necessary to open an eyelid or twitch a finger, but whose mind is still supremely sharp, potent, wielding immense magical and psychic power, and sleeplessly watches over the githzerai, even across the planes. It was he who led the gith into Limbo after the death of Zerthimon at Gith's hands, and he is revered and beloved like Zerthimon as something like a god. According to his teachings he is encourages the challenges of limbo to prove themselves worthy in Zerthimon's eyes and states that the githzerai should not simply wait for Zerithmon's return, but pave the way for him so that when Zerthimon does come back he can more easily lead them to their golden age.