"Father Time" was an Elder of the Universe, one of that rare group of figures who were among the most powerful and oldest in the universe. The race he'd come from was long-since extinct and forgotten, having dwindled to senescence and then race-death only a billion years after the birth of the universe. When "Father Time" was in full possession of his faculties--a rare occurrence--he remembered everything about his birth-race, including its name, but his memories were not fond ones. They were the abcde, a race of sentient amorphous beings of an extremely rare semi-liquid material not found within six galaxies of the Milky Way. Their home planet had been a harsh and unforgiving one full of climactic and geologic extremes, and the abcde had built their civilisation on the bottom of their world's chlorine seas. The civilisation had been concerned with survival first and then economic prosperity; attempts at artistic expression had been rare and seen as a waste of time. "Father Time," who in those days had been known as fghij--xwvumb, was a genetic freak; he was born with an imagination, a rarity in his race and something seen as a major personaity flaw. And so fghij--xwvumb was a social outcast with nothing that the abcde would consider career prospects.
fghij--xwvumb would have ended up a victim of the relentless tides of the chlorine seas or the liquid manganese creatures that swam through it, or perhaps have been caught in the maw of the tectonic plates that the abcde used as their final resting place for otherwise indestructible garbage, had his life progressed along the "normal" lines for a abcde social outcast. But he stumbled upon a device whose origin is unclear but is thought to have either been made by the legendary Founders or to have somehow survived the destruction of the previous universe. The device merged itself with the stuff of fghij--xwvumb and imbued him with high levels of cosmic energy and the ability to control and manipulate chronal energy as well as the Fourth Dimension--Time--itself.
fghij--xwvumb immediately left his home planet, which was located in an out-of-the-way system in an ordinary section of a small arm of a minor galaxy on the far edge of the galactic cluster along the rim of the Null Places. fghij--xwvumb began travelling, first in his own galaxy and then, after a millennia, in other galaxies.
For a long time fghij--xwvumb enjoyed himself and his new powers, playing the galactic tourist in a variety of shapes, seeing the many (very many) sights and experiences that the galaxy had to offer. But eventually that began to pall, as fghij--xwvumb felt the weight of the years upon him, and he looked ahead, using his powers to scan the entirety of the Fourth Dimension to see his own fate.
What he saw appalled him. He was just past his first millennia of life, and his death was not fated to come until just before the end of the universe itself. The prospect of so many long years awaiting him, like an eternity made up of rainy Sunday afternoons when there's nothing good on tv and you've nothing good to read, filled him with an almost unbearable grey depression.
He considered sending himself through time, arriving at the heat-death of the universe and so ending his own miserable existence, but even after so many years of being other races fghij--xwvumb could not escape the abcde's cultural inhibitions against suicide. It was only after some years that fghij--xwvumb came upon the solution that saved his sanity and enabled him to enjoy the rest of his existence.
What had come to bother him, regardless of the form he'd taken on and the circumstances in which he placed himself, was that he always knew that he was an all-powerful being with very little chance of being killed or even seriously harmed. As the years had rolled by he began to feel that he'd seen just about everything there was to see; different races and cultures began to remind him of ones he'd seen centuries ago. Finally nothing seemed new to him, and everything--everything--recalled the past. To go through billennia more of that was unthinkable.
Unless, of course, he wasn't aware of his future, and his real identity.
So Father Time, using his powers with enormous precision, slowed down the zone of time around a certain part of his own brain, the parts that were aware of his own final fate, and the details of his past, and the limits of his own power. He set limits on how long the time dilation would last, and when it would stop and begin, so that if he were ever in mortal danger he would snap back to full knowledge, but other than that, he'd only know that he was an alien travelling around the universe, using his powers for his own benefit and enjoyment.
And ever since then he'd visited uncountable alien races, always wearing their forms and enjoying a life or several lives among them until he finally was bored with them and moved on. Whenever he left a civilisation he always returned to his abcde form and catalogued his experiences, and then went in search of a new civilisation and new lives to live.
He'd been on Earth for only one lifetime, as "Larry Scott," and was enjoying it enormously. The death of his human father had moved him deeply and impelled him to begin fighting against human evils, evil being something depressingly common throughout the universe. He'd been flattered to have been asked to join the Liberators, and enjoyed his time with him--the fighting was so immediate and real that he sometimes forgot who he was and thought he was in actual danger. Then, when Mephisto had helped the Germans kidnap the Liberators and torture them, "Father Time" had suffered along with them, his enormous powers neutralised by the more-powerful-still spells of Mephisto. After he and the other Liberators had been rescued and recovered, his failsafes kicked in and he became fghij--xwvumb again. He decided to continue being "Father Time," but with much more awareness of his true origin and powers than he usually possessed while wearing a mortal's body.
And so he'd continued fighting alongside the Liberators, enjoying himself immensely and using his powers only sparingly (that would be cheating, after all). He hadn't bothered to use his powers when he'd first arrived on the plain of the M'krann; the sensations were so vivid, and the notion that one of these mortals could actually take control of the Crystal was so remote, that he decided to simply enjoy the experience. By the time Apocalypse seized the M'krann, it was too late. Apocalypse was in Heaven, beyond even the reach of "Father Time," but the creatures on the plain of the M'krann...they could be affected....
Author's Notes
This interpretation of Father Time is based on the events of Captain America #383.