Simulacrum With Time Travel

Question

One of the Lair Actions of a Gynosphinx is:

The flow of time within the lair is altered such that everything within moves up to 10 years forward or backward (sphinx's choice). Only the sphinx is immediately aware of the time change. A wish spell can return the caster and up to seven other creatures designated by the caster to their normal time.

Meanwhile the description of the spell Simulacrum states:

If you cast this spell again, any currently active duplicates you created with this spell are instantly destroyed.

What would happen if the below steps occur?

1. I cast the spell Simulacrum to create a copy of myself
2. My simulacrum and I were both transported 10 years forward in time by a Gynosphinx
3. Only I was transported back in time while my simulacrum is trapped 10 years in the future
4. I cast the spell Simulacrum again to create a new copy of myself

Some possible outcomes I thought of are listed below:

• The future simulacrum is destroyed the moment it is transported to the future, since I will have already created another simulacrum in the past.
• The simulacrum in the future is only destroyed when its existence in time coincides with the new simulacrum I created. (e.g my new simulacrum survives for 10 years to the date where the old simulacrum is transported to in the "future"). If a the existence of a new simulacrum does not coexist with the "future" simulacrum, the "future" simulacrum continues its existence (e.g my new simulacrum dies before the date of which my old simulacrum is transported to in the future).

What would be the most likely outcome according to RAW? Or is the most likely outcome not listed above? If the answer is based on the setting, any published adventure setting would be welcome to draw examples from (forgotten realms, dragonlance, exandria etc.)

Answer 1

It's up to the DM

And her decision will be informed by the model of time travel that they subscribe to in their campaign.

In his 2012 doctoral thesis, Models of Time Travel: a comparative study using film, by analysing over 100 feature films, Dr Guy Micklethwait identified 21 possible models of time travel (Table 19 p.195) depending on their use of two types of timeline (replacement or parallel), five timeline properties (diverging, converging, double wall, fixed, or multiple), and four past-future rules (open-open, open-closed, closed-open, or closed-closed). While this gives a total of 40 possibilities, only 21 are self-consistent.

These are the sorts of things a DM has to contend with if they are foolish enough to allow time travel in their game.

Depending on your model, either option is possible. In other models, the first would be destroyed, either instantly or when they occupy the same time period. Or both could coexist (using the word loosely) in parallel timelines. Or that each destroys the other because both castings are subsequent to each other. Or that they are, in fact, the same simulacrum. Time travel is complicated.

Answer 2

If a second duplicate survives, the original is destroyed as soon as it arrives in the future

It will depend on the metaphysics of time travel determined for your campaign - there are several versions to choose from (21, according to Dale M’s answer!). And this specific scenario isn’t really covered by the rules. But, if we assume a simple consistent model of time travel which matches the assumptions of your question - that both duplicates exist in the same “timeline”, time travel using magic like the sphinx lair is instantaneous (or time experienced during the travel “doesn’t count”), and it is not possible to alter established history - I think most likely your second interpretation is correct: the duplicate you created first is destroyed instantly on arrival in the future, but only if a second one lasts long enough to catch up with it in time.

You quote the spell stating (emphasis mine):

If you cast this spell again, any currently active duplicates you created with this spell are instantly destroyed.

Note that this is not the current language used by the spell, as I discovered on looking it up, but let’s run with that for now.

While the duplicate would be “currently active” if it were in another place, including another plane of existence (since the spell doesn’t specify a limit on range), it is not currently active - as in, active at the time you cast the spell - if displaced in time. This is because - under our assumptions - time travelling instantly to the future means it effectively doesn’t exist at all for the ten years in between its departure and destination times.

The current version of the spell is simpler; the last line now reads:

If you cast this spell again, any duplicate you created with this spell is instantly destroyed.

There’s nothing here about the duplicate being currently active, which was presumably removed to avoid a loophole for multiple duplicates by making an existing one somehow “inactive” at the time the spell was cast again. It could be argued by strict rules-as-written interpretation (RAW) that to be destroyed, a duplicate must exist when the spell is cast, if you consider that to be the “instant” referred to by “instantly destroyed”. But note that both versions of the spell say “if you cast this spell again”, not “when”, which might indicate that wasn’t the intent.

In any case I think the intent of the rules (RAI) for either version is clear: you can’t have more than one duplicate at a time created by simulacrum, so having two separated by time travel seems within the spirit of the spell. It also feels hard to abuse, since the spell doesn’t allow any special means of communication that would get around being separated by time travel - and your DM should have control over how time travel works, especially in the sphinx’s lair scenario.

The answer varies for other scenarios, assuming the same time travel rules apply:

• If another duplicate travels forward in time, and arrives after the first one’s arrival time, then by this interpretation the first one would survive until that point.
• If the duplicate had been sent ten years into the past and survived, it would exist for those ten years and continue existing until it caught up to the moment when you cast simulacrum again.
• If it was on another plane where time flows slower or faster than the one the caster is on, it might survive for a shorter or longer period than the period between their separation and the second casting of the spell, depending on when that moment aligns with the time of the other plane.