Does being under the effect of more than one Sanctuary spell require more than one saving throw?

Question

The description of the sanctuary spell says (PHB, p. 272):

You ward a creature within range against attack. Until the spell ends, any creature who targets the warded creature with an attack or a harmful spell must first make a Wisdom saving throw. On a failed save, the creature must choose a new target or lose the attack or spell. [...]

Does being under the effect of more than one sanctuary spell require more than one saving throw?

In the case where there are two clerics who cast sanctuary on the same PC:

• would a monster trying to attack the character need to succeed on two separate Wisdom saving throws (one against each casting) in order to attack?
• or, would the monster only need to succeed on one saving throw against the cleric with the higher spell save DC in order to attack?

If you refer to the rules on combining spell effects in your answer, please explain your reasoning.

Answer 1

A creature cannot be actively affected by two instances of the same spell, this includes the warded creature; one saving throw is made

The rules on "Combining Magical Effects" state:

[...] The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect—such as the highest bonus--from those castings applies while their durations overlap, or the most recent effect applies if the castings are equally potent and their durations overlap [...]

In this case we have the same spell (sanctuary) cast multiple times and thus the castings don't combine on the target (the warded creature). This means that the target of the sanctuary spells can be actively benefiting from only one instance of sanctuary at a time; the "more potent" one will be active.

Which instance of sanctuary is "more potent" is entirely left up to the GM. The example given is the spell that has the highest bonus, but that's only one possible case. The GM can decide which effect is considered "more potent"

That said, both castings of sanctuary are still there. So if one were removed by some means, the second one would then be the active spell on the creature.

Answer 2

The Combining Magical Effects section of the Basic Rules states:

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect — such as the highest bonus — from those castings applies while their durations overlap, or the most recent effect applies if the castings are equally potent and their durations overlap.

For example, if two clerics cast bless on the same target, that character gains the spell's benefit only once; he or she doesn't get to roll two bonus dice.

Therefore if two clerics each cast sanctuary on you, only one of them is actually applied: the one with the higher spell save DC. While there are multiple castings of sanctuary on the same target, a creature has to make only one saving throw to be made if it tries to attack the target of the spell.