Elspeth von Draken
A character released by Forgeworld for Warhammer Fantasy (back when FW knew Warhammer Fantasy existed) for The Empire army as part of its Tamurkhan: Throne of Chaos campaign book. She has very little lore, only one paragraph, and has never featured in an important role in any Warhammer Fantasy novelization.
Despite this she is a fan-favorite due to having an absolutely BEAUTIFUL model known for it's detail and good casting. To date she's the only one who isn't a gay Catholic space Nazi who can pull off the "skull-faced cherub sidekick" look.
It's important to note her name is "Elspeth" not "Elizabeth", because it's unlikely you'll remember it right without that.
Her lore: "For generations the name of Elspeth von Draken, Magisterix of the Amethyst College and arch-wizard of the Lore of Death, has been spoken of in hushed tones in the reeking tavern gutters and vaulted noble halls of Nuln alike. Yet despite these stories few have ever paused to think what exactly the admitted presence of von Draken in the city actually means, and fewer yet could guess at her true power or influence. Furthermore the few foolhardy or overenthusiastic witch hunters, unaware of her relationship to the governing powers of Nuln or too fanatically sure of their own righteousness to care, who have attempted to delve deeper into her business or storm her tower have been swallowed up so completely that they have never been able to share anything they have learned. "
From her special rules we get: (Darkwalker) "Von Draken’s body has become so suffused with dread magical power to the extent that she stands halfway between life and death-"
(Coruscating Blast) "The Carmine Dragon’s breath weapon is a sorcerous blast of powerful Amethyst magic capable of withering metal and rendering flesh to dust as if millennia had passed in mere seconds."
(The Pale Scythe) "A pale scythe more made of shadow than substance, this weapon said to be of Elspeth’s own making is attuned to the power of Shyish, the wind of death, focusing and concentrating it to her will."
(Death's Timekeeper) "This hourglass is an ancient and storied artefact, it is said to contain as its measuring sand the dusty remnants of a dead god of old, and Van Draken has spent much of her unnaturally long life studying its mysteries. With it she has perfected some limited measure of control over time and death itself. "
She vanishes after Tamurkhan is destroyed (seemingly dying due to how she fades away) and her dragon dies on the spot and gets no mention in any official lore after that point.
Elspeth sadly got no mention in the End Times, but one of GW's better writers came to the rescue with some lore-mending (making it as official as any writefaggotry). As an amethyst wizard, Elspeth suffered the same fate as the rest of her lot when Nagash freed the Wind of Death. However, she had been well along that path already before Nagash's actions, already beginning to succumb to the unholy changes. But given her raw power, she was able to weather it better than most and stayed in control and true to her course. She escaped the destruction of Nuln and was one of the few remaining Empire wizards of any real ability when Archaon came knocking on Averheim's walls. Elspeth, like Ungrim Ironfist and Mathias Thulmann, died in the ensuing battle against Archaon's forces.
Whether she stayed dead, well...that's another matter.
On The Tabletop
Elspeth has absolutely AMAZING stats. For only 590 points (unfortunately becoming the ENTIRE Lord allowance, and only being able to be taken in non-End Times rules games at 2360 points or above (so basically at 2500 and up)) you get a Dragon comparable to a High Elf Star Dragon with a rider of average survivability who is Loremaster (has all spells) in one of the best lores in the game (Death, in case you skipped the above section). Her Darkwalker rule grants her Immune to Psychology and makes all To Wound rolls against her are made at -1, although the drawback (or possible advantage?) is that she counts as Undead and Daemonic so Lore of Light can wreck her day. Her Magic Weapon gives her Killing Blow (not as effective) and her Dispel rolls are at +1 (not exactly a big boon, but a nice one to have).
Her best trick however comes from her magic item that allows her to reroll one dice per PLAYER turn (meaning once on yours, once on your opponent's, and once for each additional player on their turn for 3+ matches). You can then choose to use this reroll or leave the result as-is, and if you don't use it? She heals one Wound. While she only has 3 Wounds total and isn't exactly armored (like, at all) this is still among the greatest rules in the entire game.
Oh, and on top of all that? The Dragon's Breath Weapon is functionally a cannon that cannot Misfire.
The only downside to this character is the model costs a whopping £74.00 (or $115.95 in the US). This model isn't quite Tau Manta bad, but it's still a chunk of change. The appearance is more justifiable however, and Elspeth herself is not attached to her base and can be placed on a horse model to function as an Archmage so the price is a bit less painful (by about $15, assuming you can get a horse miniature somewhere cheap).
Age Of Sigmar
She's still dead, but you can make some nice conversions out of her for Cities of Sigmar. Maybe hold back on the hobby knife though, these forge world characters have a hard time staying dead.