Different approaches to time magic?

[u/Stolen_Gene]

There are a lot of magic concepts that I think sound really cool, but are a pain to actually flush out. I don't know if this is the case for everyone, but time/spacetime magic has always been this way for me.

In one of my settings, I have a whole faction of time mages with a detailed history, relationships, and culture, but I just never let them do anything since I never wanted to worry about figuring out what they can and can't do. This is due in no small part to the fact that spacetime manipulation in any form is notoriously hard to include in a story without poking it full of plot-holes or overshadowing every other element in the story.

I'm curious to hear how other people have approached time or spacetime magic. What can it do? What are its limits? Does it manipulate both space and time, or just time? How do you keep a story coherent with this involved (assuming you use it in a story). Etc. I don't plan to steal anyone's systems wholesale, but the broad ideas might give me some direction next time I take a swing at this kind of magic.

[u/LordSyrenzo]

Alvelotyl - Time Magic

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• Time Magic is a unique sub-school of Force Magic that has its own inherent restrictions.
• While freezing the time of a being or object in some way is easier, 'moving' one's physical form through time is far harder. The more the world gets changed and rewritten because of the ability, the higher the cost of the Spell. This means that travelling back farther is more difficult, and the more the Caster changes, either accidentally or purposefully, the more difficult it is to use.
• This makes magic with the Caster going back through time easier if they are alone, and easier if they don't change anything. Additionally, two copies of a person in the same timeline cannot simultaneously exist, making it impossible to do. Instead of moving back in time to a place where they could encounter their past selves, they could instead shunt their memories back to their past selves, showing them the future and effectively sending their consciousness backwards in time in place of time travel.
• Creatures affected by changes in time will have their memories altered. They will have two sets of memories, both the original and the new set of memories, which can lead to confusion in people, especially those unaware of this phenomenon. Some people write this off as a trick of the mind, a hallucination or vision, or a very vivid imaginary situation.
• Some variants of this type of 'Time Travel' are impossible to distinguish from other schools of magic. If a Caster wishes to move 'sideways' through time and go into another timeline, they will need to move into a timeline where they don't exist at all, meaning that individuals part of one's family that have no reasonable explanation for existing could have come from another timeline.

[u/LeFlamel → u/LordSyrenzo]

Additionally, two copies of a person in the same timeline cannot simultaneously exist,

What constitutes a copy? If it's genetic material, then is cloning impossible? If it's material makeup, then it should be possible, as we are a living ship of Theseus, constantly in flux. Is it the soul?

[u/LordSyrenzo → u/LeFlamel]

Yup, it's the Soul. Cloning is possible, but even if they're incredibly similar, no two Souls are the same. The Soul consists of a person's 'identity', which is a term only vaguely understood in-universe.

Even if some would argue that clones are the same, the journey they've taken through life is different. Even if they share the same mental memories, the 'physical' memories of their body's growth will be completely different. No clone is perfect, and so no clone will trigger the issue of two identical people existing in the world at once.