Magical Life Extension is the use of magic to halt, or even reverse, aging. It also encompasses the use of psychic magic to obtain control over the processes of memory retention. It was heavily restricted during the Golden Age, but has been historically common among magic users from the Pre-classical Period to the present. Magical life-extension has its limits in terms of the achievable duration; it is difficult to apply to persons other than the caster. Still, the obvious allure has resulted in many a deal between a rich pony and an unscrupulous mage willing to try her horn at it, to variable results.
There are various known complications of repeated magical life extension. Due to the accumulation of disabling complications (or, occasionally, simply due to ennui), most practitioners choose not to extend their life beyond two centuries. Bluestar the Brilliant, however, is reported to have lived over eight hundred years before succumbing to an unexpected, fatal complication in 2835 AE.
True Alicorns such as the legendary Princesses were supposed to have been immortal, although the nature of this everlasting life is subject to speculation.
The Undead and spirits are also thought to be immortal. Fortunately, little of them is known on the Isle of Yore.