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In 5e, things that refer to magic only interact with entities that have/are magic as part of their crunch, not fluff. To determine if something is actually magic, rather than described as magic but totally not actually magic, use the rule on page 17 of the 2017 Sage Advice Compendium page 17 of the 2017 Sage Advice Compendium:

our[O]ur game makes a distinction between two types of magic:  

• the background magic that is part of the D&D multiverse’s physics and the physiology of many D&D creatures
• the concentrated magical energy that is contained in a magic item or channeled to create a spell or other focused magical effect

  • the background magic that is part of the D&D multiverse’s physics and the physiology of many D&D creatures
  • the concentrated magical energy that is contained in a magic item or channeled to create a spell or other focused magical effect

In D&D, the first type of magic is [fluff]  ... The second type type of magic is what the rules are concerned about. When a a rule refers to something being magical, it’s referring to that that second type. Determining whether a game feature is magical magical is straightforward. Ask yourself these questions about about the feature:

• Is it a magic item?
• Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
• Is it a spell attack?
• Is it fueled by the use of spell slots?
• Does its description say it’s magical?

  • Is it a magic item?
  • Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
  • Is it a spell attack?
  • Is it fueled by the use of spell slots?
  • Does its description say it’s magical?

If your answer to any of those questions is yes, the feature is is magical.
Let’s

Let’s look at a white dragon’s Cold Breath and ask ourselves those questions. First, Cold Breath isn’t a magic item item. Second, its description mentions no spell. Third, it’s not not a spell attack. Fourth, the word “magical” appears nowhere in its description. Our conclusion: Cold Breath is not considered considered a magical game effecteffect[.]

(Note that 'described as magic' here means something other than what it normally means, since Whitewhite dragons, as the entry notes before this passage, are described as magical. It seems like the author means 'in its description' to mean 'in the part of its description where the rules go, you know, its actual description', - but that is contrary to how the authors have claimed you should read spells etc(etc.) to prevent certain kinds of textual ambiguities and errors from being problems, so make of it what you will.)

This is a helpful starting place, but not sufficient; we still don't know how instantaneous spells with long durations or secondary effects of spells work. For the former, it helps that the rules say about instantaneous spells:

Many Spellsspells are Instantaneousinstantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can’t be dispelled, because its magic exists only for an instant.

In 5e, things that refer to magic only interact with entities that have/are magic as part of their crunch, not fluff. To determine if something is actually magic, rather than described as magic but totally not actually magic, use the rule on page 17 of the 2017 Sage Advice Compendium :

our game makes a distinction between two types of magic:  

• the background magic that is part of the D&D multiverse’s physics and the physiology of many D&D creatures
• the concentrated magical energy that is contained in a magic item or channeled to create a spell or other focused magical effect

In D&D, the first type of magic is [fluff]... The second type of magic is what the rules are concerned about. When a rule refers to something being magical, it’s referring to that second type. Determining whether a game feature is magical is straightforward. Ask yourself these questions about the feature:

• Is it a magic item?
• Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
• Is it a spell attack?
• Is it fueled by the use of spell slots?
• Does its description say it’s magical?

If your answer to any of those questions is yes, the feature is magical.
Let’s look at a white dragon’s Cold Breath and ask ourselves those questions. First, Cold Breath isn’t a magic item. Second, its description mentions no spell. Third, it’s not a spell attack. Fourth, the word “magical” appears nowhere in its description. Our conclusion: Cold Breath is not considered a magical game effect

(Note that 'described as magic' here means something other than what it normally means, since White dragons, as the entry notes before this passage, are described as magical. It seems like the author means 'in its description' to mean 'in the part of its description where the rules go, you know, its actual description', but that is contrary to how the authors have claimed you should read spells etc to prevent certain kinds of textual ambiguities and errors from being problems so make of it what you will)

This is a helpful starting place, but not sufficient; we still don't know how instantaneous spells with long durations or secondary effects of spells work. For the former, it helps that the rules say:

Many Spells are Instantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can’t be dispelled, because its magic exists only for an instant.

In 5e, things that refer to magic only interact with entities that have/are magic as part of their crunch, not fluff. To determine if something is actually magic, rather than described as magic but totally not actually magic, use the rule on page 17 of the 2017 Sage Advice Compendium:

[O]ur game makes a distinction between two types of magic:

  • the background magic that is part of the D&D multiverse’s physics and the physiology of many D&D creatures
  • the concentrated magical energy that is contained in a magic item or channeled to create a spell or other focused magical effect

In D&D, the first type of magic is [fluff]  ... The second type of magic is what the rules are concerned about. When a rule refers to something being magical, it’s referring to that second type. Determining whether a game feature is magical is straightforward. Ask yourself these questions about the feature:

  • Is it a magic item?
  • Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
  • Is it a spell attack?
  • Is it fueled by the use of spell slots?
  • Does its description say it’s magical?

If your answer to any of those questions is yes, the feature is magical.

Let’s look at a white dragon’s Cold Breath and ask ourselves those questions. First, Cold Breath isn’t a magic item. Second, its description mentions no spell. Third, it’s not a spell attack. Fourth, the word “magical” appears nowhere in its description. Our conclusion: Cold Breath is not considered a magical game effect[.]

(Note that 'described as magic' here means something other than what it normally means, since white dragons, as the entry notes before this passage, are described as magical. It seems like the author means 'in its description' to mean 'in the part of its description where the rules go, you know, its actual description' - but that is contrary to how the authors have claimed you should read spells (etc.) to prevent certain kinds of textual ambiguities and errors from being problems, so make of it what you will.)

This is a helpful starting place, but not sufficient; we still don't know how instantaneous spells with long durations or secondary effects of spells work. For the former, it helps that the rules say about instantaneous spells:

Many spells are instantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can’t be dispelled, because its magic exists only for an instant.

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In 5e, things that refer to magic only interact with entities that have/are magic as part of their crunch, not fluff. To determine if something is actually magic, rather than described as magic but totally not actually magic, use the rule on page 17 of the 2017 Sage Advice Compendium :

our game makes a distinction between two types of magic:

• the background magic that is part of the D&D multiverse’s physics and the physiology of many D&D creatures
• the concentrated magical energy that is contained in a magic item or channeled to create a spell or other focused magical effect

In D&D, the first type of magic is [fluff]... The second type of magic is what the rules are concerned about. When a rule refers to something being magical, it’s referring to that second type. Determining whether a game feature is magical is straightforward. Ask yourself these questions about the feature:

• Is it a magic item?
• Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
• Is it a spell attack?
• Is it fueled by the use of spell slots?
• Does its description say it’s magical?

If your answer to any of those questions is yes, the feature is magical.
Let’s look at a white dragon’s Cold Breath and ask ourselves those questions. First, Cold Breath isn’t a magic item. Second, its description mentions no spell. Third, it’s not a spell attack. Fourth, the word “magical” appears nowhere in its description. Our conclusion: Cold Breath is not considered a magical game effect

(Note that 'described as magic' here means something other than what it normally means, since White dragons, as the entry notes before this passage, are described as magical. It seems like the author means 'in its description' to mean 'in the part of its description where the rules go, you know, its actual description', but that is contrary to how the authors have claimed you should read spells etc to prevent certain kinds of textual ambiguities and errors from being problems so make of it what you will)

This is a helpful starting place, but not sufficient; we still don't know how instantaneous spells with long durations or secondary effects of spells work. For the former, it helps that the rules say:

Many Spells are Instantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can’t be dispelled, because its magic exists only for an instant.

That means that all the magic after the instant the spell is cast is fluff magic instead of crunch magic. We run this as all the magic stuff happening in a sequence of moments that nonetheless as a whole paradoxically takes up no time. This is important as a naive ruling that such spells do the magic first and then the rest of the seemingly magical effects happen leads to undesirable behavior like being able to fireball people inside an anti-magic field.

For secondary effects of spells, you're just going to have to make a ruling. A summoned creature should probably be magical, grass that caught fire from produce flame and then spread to a house probably should not be. The bullet point that makes them magical is the 'fuelled by spell slots' line, so the more that seems to be true the more it should count, presumably.