You can normally take reactions on your own turn, which includes reacting to things you are doing to yourself.
Note though that Featherfall isn't reacting to a spell you cast; it's reacting to you falling. It shouldn't make a difference whether you step off a cliff or cast a spell; one of its designed uses is to save you from splattering when you find ...
It depends on your table
"Reactions" are a game concept, it's not something your character is aware of. So it depends entirely on what kind of seperation of in-character and meta-knowledge your game table uses.
There is no real right or wrong answer here, even if you do not allow meta knowledge, your character might still be able to realize this fact ...
Protection does not grant additional opportunity attacks
The Protection is one of the options for a Fighter's fighting style. It allows, exactly as you quoted, to use one's reaction to impose disadvantage on enemy attack rolls under certain conditions. It doesn't say anything about giving additional ways to make an opportunity attack, and hence it doesn't ...
Depending on the context of the encounter, the following quote from the PHB, page 189, might be relevant:
If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends.
So if the Rogue's sneaky stabby is the start of the combat and the Wizard wasn't expecting him, ...
Reactions can be taken on your turn.
A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's.
Therefore, yes, you can cast Shield as a reaction if you provoke an opportunity attack on your turn.
There are abilities/actions that use "reactions" that don't need to be prepared. Opportunity attacks are attacks that use your reaction, but don't have to be prepared before it is taken. You just get to decide if you want to use your reaction to make an opportunity attack when/if an enemy leaves themselves open for one.
There are also some spells (the 1st ...
You only have one reaction per round
The bottom line here is that a PC only has one reaction, as kviiri's answer also states. From the rules of Reactions:
When you take a reaction, you can't take another one until the start of your next turn. If the reaction interrupts another creature's turn, that creature can continue its turn right after the reaction.
You've already stated the key point:
1 reaction, which you take when you are hit by an attack or targeted by the magic missile spell.
So what you need to understand here is that the Shield spell involves time travel. No, really, it does. You can cast Shield when you're hit by an attack. Not when you're targeted, or when someone tries to attack you, but ...
The narration of the event seems strange to you because you are confusing the planned order of events with the actual order of events.
The plan was that the encounter begins when A throws their dagger. So if the characters had followed the plan then the order of events for round 1 would have been:
X does nothing because they don't know they are in an ...
Unfortunately, as awesome as this sounds, by the rules, it doesn't work. Hellish Rebuke is a reaction that you take
in response to being damaged
Not "in response to being hit", or "in response to being attacked". You actually have to take damage to use it.
Whenever a creature takes damage, that damage is
subtracted from its hit points.
You haven't ...
Reactions come after their triggers, except when they don't
If the timing is specified in the ability, use that timing. Otherwise, reactions occur after the trigger.
This entire thing is a matter of specific over general. In 5e, when a specific rule and a general rule conflict, the specific rule wins.
Xanathar's Guide to Everything outlines the general ...
You are correct, reaction spells cannot be readied or precast
Reaction spells are cast as a reaction in response to a trigger that is spelled out in the spell description. In the case of shield, that trigger is "when you are hit by an attack or targeted by the magic missile spell". When that triggers occurs, you can cast the spell and spend the spell slot ...
Nothing in the ready or opportunity attack rules suggest that they're mutually exclusive beyond using one's reaction, which is only used when actually making the opportunity attack or taking the readied action. Therefore, you can forgo the option to use the readied fireball to make an opportunity attack if you wish and circumstances permit.
Using one's ...
The rules for reactions are fairly straightforward:
Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's. The opportunity attack, described later in this section, is the most common type of ...
The rules for Multiattack in the Monster Manual (page 11) are perfectly clear:
A creature that can make multiple attacks on its
turn has the Multiattack ability. A creature can’t use
Multiattack when making an opportunity attack, which
must be a single melee attack.
Or, in other words, it works exactly the same way as Extra Attack, and can't be ...
According to this tweet by Mike Mearls, you're supposed to know with certainty whether the shield is enough to protect you or not, so that you can't waste the spell, unless you choose to:
Querent: Am I right..Wiz should know roll before using Shield,cant 'waste it' from not knowing roll?
Mike Mearls: correct
This is also how I have seen it be done ...
Yes, That Description is RAW
That is the way mechanics happens in RAW. How you narrate that to make sense is up to you. Remember the rules have to be turn based to make it run and everything that happens in a round is happening inside 6 seconds and at roughly at the "same time".
Two Common Alternatives
There are two common alternatives I've seen:
If the casting time of a spell is 1 reaction, you can only cast it using your reaction (unless you benefit from a special feature that lets you do otherwise). This is because there is no general rule that lets you change the casting time of a spell from 1 reaction to 1 action.
There's nothing I can cite that confirms that because it's impossible to ...
The hostile creature’s movement doesn't provoke an opportunity attack from you, so your War Caster feat isn't triggered.
The War Caster feat (PHB 170) says:
When a hostile creature’s movement provokes an opportunity attack from
you, you can use your reaction to cast a spell at the creature, rather
than making an opportunity attack. The spell must ...
You can't take both Dash and Ready actions
Normally you don't "prepare a reaction". You take the Ready action instead. See Player's Handbook, page 193, "Actions in Combat"
Sometimes you want to get the jump on a foe or wait for
a particular circumstance before you act. To do so, you
can take the Ready action on your turn so that you can
act later ...
You already bolded the answer.
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
If you're not taking the Attack action on your turn, then you can't use Extra Attack. Taking the Attack action doesn't just mean attacking - it's a specific action you can perform, listed under Actions in Combat.
Reactions can interrupt multiattack.
The rules on reactions says:
A reaction is an instant response to a trigger of some kind, which can
occur on Your Turn or on someone else’s. [...] If the reaction
interrupts another creature’s turn, that creature can continue its
turn right after the reaction.
Multiple attacks on one turn are ...
No, War Caster doesn't let you do this
Unfortunately, the benefit that War Caster offers is specifically that:
When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only ...
Whether it hits
Usually, the DM asks your AC before the play, and they take a note behind the screen. When they roll an attack behind the screen, they can immediately determine whether it hits or not. In this style, the DM only announces the hit, and not the total roll.
your group has been using the other style: announcing the total attack roll.
The hydra can take them all at the same time in response to a single trigger or pace them out over a round in response to multiple triggers.
Here's the text of the feature we're talking about (from the hydra's stat block):
Reactive Heads. For each head the hydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.
Casting a Reaction spell does not interrupt a spell with a long cast time, regardless of spell components. (As long as it isn't a Concentration Spell)
The rules for spells with a long casting time are...
Certain spells (including spells cast as rituals) require more time to cast: minutes or even hours. When you cast a spell with a casting time longer ...
When you take damage.
The casting time of absorb elements (Elemental Evil, 150) is with my emphasis:
Casting Time: 1 reaction, which you take when you take acid, cold, fire, lightning, or thunder damage
This means that the trigger is when you take damage, and that is when you can cast the absorb elements. Not before, not later.
Being targetted, making ...
Short answer: Yes, you can take a reaction before your first turn in combat.
Reactions and bonus actions aren't ever something you “have”, they're something you do. And there is a limit on the number of times in a round that you can do them.
As a consequence, it doesn't make sense to ask if you “have” either one when you are surprised. What matters is ...
Yes you could dispel it, but the initial attack would still miss
The DMG has guidance on when Readied actions (and reactions and triggers in general) occur:
follow whatever timing is specified in the reaction's description. For example, the opportunity attack and the shield spell are clear about the fact that they can interrupt their triggers. If a ...
It is not redundant
There are many ways you could take damage on your turn, thus allowing you to use Misty Escape as a reaction on your turn in addition to (before) your Action and possible Bonus Action:
An enemy was holding an attack or damaging spellcast that is triggered before you attack or cast a spell on your turn.
Many ability/spell effects also ...