[RPG] If I cast Darkness at 4th level and someone else casts Daylight at 4th level, how do the two spells interact

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If I cast Darkness at 4th level and someone else casts Daylight at 4th level, how do the two spells interact?

I found this Twitter post by Jeremy Crawford back in October 2014 that says the spell does not get stronger when upcast, but as is written in the Player's Handbook (p. 201):

When a spellcaster casts a spell using a slot that is of a higher
level than the spell, the spell assumes the higher level for that
casting.

Therefore, if we both cast Darkness and Daylight at 4th level, they do not dispel each other – but how would they interact when they meet each other?

Best Answer

Neither daylight nor darkness is dispelled.

Under the entry for darkness in the Player's Handbook, we see:

If any of this spell’s area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled.

And under the entry for daylight in the Player's Handbook, we see a similar:

If any of this spell’s area overlaps with an area of darkness created by a spell of 3rd level or lower, the spell that created the darkness is dispelled.

Neither of these spells contain an "At Higher Levels" clause allowing them to dispel higher leveled opposing luminosity spells, so casting them at higher levels only protects them from being dispelled.

So, we know they don't dispel one another, but as you've asked, what exactly happens in the space where the spells overlap?

Daylight prevails.

Again, under the entry for darkness in the Player's Handbook, we see:

A creature with darkvision can’t see through this darkness, and nonmagical light can’t illuminate it.

Daylight is certainly magical light, so it is not hindered by darkness.

Similarly, continual flame can be cast from a 3rd level spell slot to create a torch whose light pierces magical darkness.