How can you get advantage from invisibility if attacking ends it?

Question

Monsters or players can have the ability to become invisible, as per the Invisibility spell. In the rules, it's said that an invisible/unseen creature gets advantage on its attacks, and enemies attacking it do so at disadvantage.

Page 194 of the PHB says, under "Unseen Attackers and Targets":

When you attack a target that you can’t see, you have disadvantage on the attack roll. This is true whether you’re guessing the target’s location or you’re targeting a creature you can hear but not see. If the target isn’t in the location you targeted, you automatically miss, but the DM typically just says that the attack missed, not whether you guessed the target’s location correctly.

When a creature can’t see you, you have advantage on attack rolls against it.

But the Invisibility spell says that you lose invisibility when making an attack or casting a spell:

A creature you touch becomes invisible until the spell ends. [...] The spell ends for a target that attacks or casts a spell.

1st question:

• Does an invisible creature lose the advantage/disadvantage when making an attack?
• Or always have advantage for his attack, but lose disadvantage versus an (opportunity) attack of the enemy?
• If he always has advantage, what happens if he has multiple attacks?

2nd question:

• In case of a pixie or a faerie dragon, who have Superior Invisibility, does the invisibility still remain?

  Superior Invisibility. As a bonus action, the dragon can magically turn invisible until its concentration ends (as if concentrating on a spell).

(Note: You can attack without losing concentration.)

Answer 1

Clarifications

The advantage/disadvantage happens when a creature can't be seen - being invisible is one way of doing this but it is not the only way - being hidden or in the dark or having a blinded opponent are other ways. See What advantages does hiding have? Because of this I will use "unseen" when I mean that the creature cannot be seen for any reason and "invisible" when I am talking about having that particular state.

You have used the word "(opportunity)" in a way which makes me think that you are coming from an older version of D&D where casting a spell could trigger an opportunity attack; this does not happen in 5e! The only trigger for an opportunity attack using a reaction is if a seen creature voluntarily moves out of another creatures reach without taking the Disengage action (PHB p. 195).

Answers

Two things to keep in mind:

1. The sequence of events goes: attack or cast spells then lose invisibility.
2. Each attack occurs at its own time - there are no simultaneous events.

If you keep that in mind then all becomes clear the creature :

1. gets advantage if it is unseen when it attacks, and
2. causes disadvantage if it is unseen when it is attacked.

Question 1

1. The creature gets advantage when it makes an attack while unseen - it then loses invisibility.
2. when the creature is attacked disadvantage happens if it is unseen at the time of the attack - this does not cause it to lose invisibility.
3. See 1. above. If a creature then attacks again it is no longer invisible (it could still be unseen e.g. a creature with darkvision attacking one without in the dark); so see 1. above.

There are all sorts of sequences that can affect this, for example:

• you are invisible at the start of your turn and can attack twice when using the full attack action and can cast invisibility as a bonus action. I am not aware of any creature that can do this but its theoretically possible.
• You move 10 feet,
• Take the Attack action and attack with advantage because you are unseen,
• turn visible,
• you use your bonus action to turn invisible,
• move 10 feet to another opponent; you do not trigger an Opportunity attack because you are unseen,
• attack then with advantage because you are unseen,
• that opponent has taken the Ready action to "attack the first creature that attacked them", they attack with no advantage or disadvantage as you are now seen.

Question 2

In D&D 5e things do exactly what they say the do; no more, no less. Just because an ability and a spell cause the same effect does not mean they have anything to do with one another beyond that.

Superior Invisibility. As a bonus action, the dragon can magically turn invisible until its concentration ends (as if concentrating on a spell).

This does not refer in any way to the spell Invisibility! The limitation on attacking and spell casting applies to the spell; it does not apply to this ability. This ability ends when the faerie dragon stops concentrating - they can otherwise attack and cast spells and remain invisible.

Answer 2

Advantage/Disadvantage is determined prior to the attack. You have it, become visible, still have it, then attack.

So to answer your questions:

1. Yes, but they retain the benefits of being invisible until after the attack. Yes you'd have it for the attack, but for any reprisal you'd be visible. In the case of a multi-Attack, I believe you'd have advantage for the first attack, but lose it for subsequent attacks.

2. This invisibility does not appear to be conditional upon not attacking(I believe the greater invisibility spell also does not have the no attacking rider), so you'd stay invisible.