Can the Chronurgy wizard's Chronal Shift feature be used when a creature uses Legendary Resistance to succeed on a saving throw?

Question

The Chronurgy Magic wizard's Chronal Shift feature (Explorer's Guide to Wildemount, p. 184) says:

You can magically exert limited control over the flow of time around a creature. As a reaction, after you or a creature you can see within 30 feet of you makes an attack roll, an ability check, or a saving throw, you can force the creature to reroll. You make this decision after you see whether the roll succeeds or fails. The target must use the result of the second roll.

Can the Chronurgy wizard's Chronal Shift feature be used when a creature uses Legendary Resistance to succeed on a saving throw?

Using the adult red dragon as an example, Legendary Resistance reads:

If the dragon fails a saving throw, it can choose to succeed instead.

Specifically, here is the scenario:

1. Wizard casts a spell that requires a saving throw on Red Dragon
2. Red Dragon rolls the saving throw and fails
3. Red Dragon expends one use of legendary resistance to succeed on the saving throw
4. Wizard uses their reaction to use Chronal Shift to force the dragon to reroll the saving throw
5. Red Dragon rerolls the saving throw and fails
6. Red Dragon expends a second use of legendary resistance to succeed the saving throw

In particular, is step 4 of this scenario a valid use of the Chronurgy wizard's Chronal Shift feature?

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For transparency, this question is a rewrite of this closed question, having this meta post about its closure. In response, I made this meta post that is more generally concerned with re-asking questions that were closed per our "don't guess the system" policy. Please avoid any meta discussion on this post, instead relegating it to the relevant meta posts.

Answer 1

Once Legendary Resistance is applied, Chronal Shift has no trigger.

Chronal shift reacts to seeing whether the roll succeeds or fails. The roll occurs, you hear from the DM what the result is, and you use a power, which (probably) changes the roll.

Legendary Resistance reacts to failing the save. The roll occurs, the save is failed, and it chooses to succeed instead... but there's no further roll generated.

Chronal Shift reacts to "completed roll", not "passed save". Thus, once Legendary Resistance has been applied, its time has already passed.

Answer 2

Yes, you can use it to force a re-roll, but it doesn't change the result.

It is important to note that Legendary Resistance does not change the actual number rolled on the die, nor does it change the fact that a die has been rolled in the first place,, it only changes the outcome of that roll.

When a creature with Legendary Resistance chooses to succeed on a save, the roll no longer matters. The result on the die can be a 1 or a 20, but once Legendary Resistance has been invoked, the number on the die no longer matters. They succeed, period.