Where and How are the legendary characters during Rime of the Frostmaiden?

I’m DMing ROTF for players that have a very deep knowledge of the lore of the Forgotten Realms, it doesn’t bother me at all, but I would like at least to be prepared enough anyway to properly address the campaign theme. I’ve read "The Crystal Shard", and keep digging into wiki and other sources of lore, but there is still a lot of things that I don’t know for sure.

Massive spoiler for the Forgotten Realms books or some other campaign books.

About Bruenor, Catti-Brie & Regis:

About Drizzt:

About the Dwarf, and more specifically the Battlehammer clan?

Overall do you have any advice on how to proceed with lore accuracy in the campaign, and some sources of lore I could read in preparation

Can a player controlling an NPC use its Legendary Actions?

Let’s say my players used Dominate Monster on a Kraken:

While the creature is Charmed, you have a Telepathic link with it as long as the two of you are on the same plane of existence. You can use this Telepathic link to issue commands to the creature while you are conscious (no action required), which it does its best to obey.

Or my Necromancy Wizard successfully commanded Stradh:

If it fails, it becomes friendly to you and obeys your commands until you use this feature again.

Can the player have the creature use its legendary actions, lair actions, and regional effects?

I’m aware that spells like True Polymorph don’t allow this. I wondered whether these do (or should!).

Why does the rogue’s Greater Weapon Specialization specify legendary proficiency?

The rogue’s level 15 class feature specifies:

Your damage from weapon specialization increases to 4 with weapons and unarmed attacks in which you’re an expert, 6 if you’re a master, and 8 if you’re legendary.

How can a rogue get legendary proficiency in any weapon? As far as I’m aware, only the fighter reaches legendary proficiency with weaponry, but a fighter will never be able to qualify for this feature because it comes directly from the rogue’s list of class features rather than a rogue feat. Consequently, the two states:

  1. Has legendary proficiency
  2. Has access to this feature

seem mutually exclusive. Is there something I’ve missed?

Do Strahd Von Zarovich legendary actions movement trigger sunlight damage?

i read this quesion about legendary actions do not trigger effects from spells that happen at the beginning of the monster turn, but since I’m playing in curse of strahd, i wondered: does strahd von zarovich, that can do legendary action and move out of its turn, can run (as a legendary action) in the sunlight with no damage ? since the sunlight do damage only when he start his turn in the area of effect (and not like moonbeam spell when he go inside it).

Can Legendary Actions be used after a dead creature’s turn?

If a monster has Legendary Actions, can it use one at the end of a dead creature’s turn? And would it matter if the dead creature is an ally of the monster or a PC?

Relevant section from the Monster Manual:

A legendary creature can take a certain number of special actions — called legendary actions — outside its turn. Only one legendary action option can be used at a time and only at the end of another creature’s turn. A legendary creature regains spent legendary actions at the start of its turn. It can forgo using them, and it can’t use them while incapacitated or otherwise unable to take actions. If surprised, it can’t use them until after its first turn in the combat.

Do creatures with Legendary Resistance know what is hitting them in order to choose to use the resistance or not?

Say I cast a Fireball at a white dragon, it definitively knows that the spell cast was a Fireball, with all those flames around…

However, some spells are more subtle, such as Banishment. Maybe the characters want to have about 1 minute to build something that will kill the dragon once it returns… but then it could take casting the Banishment spell (or other spells) many times to successfully sending the dragon on a demiplane for a while.

Yet, if the Dragon (or other target) cannot really know what the spell is, then it could accept a failure thinking it may need its resistance later when it is in a worst situation than at this time…

I have not been able to find something in RAW that says the target knows of the exact spell effects when it has the Legendary Resistance skill. Is there?

Scrying on a creature with legendary resistance

My players recently decided that they would like to cast the Scry spell on a creature that has the Legendary Resistance trait.

Does this trait function outside of combat?

My major concern is that the creature wouldn’t necessarily know it was being scryed on in order to use the resistance to avoid it. In combat, a creature could see a (for example) fireball coming and decide to avoid it, but with no indicator at all that a spell was targeting the creature, it is less clear to me.

Can a Legendary with the Nature/Oceans/Sky Aura summon itself?

In the Blessed and the Damned, Legendary Pokémon are given auras that grant special abilities to make them even more formidable. Three of these allow the user to summon a combatant of a level equal to their own (Or half their level if the combatant is a trainer).

I can not find any limitations to these combatants other than the level. Could this aura be used to summon an exact duplicate of the Legendary in question? I understand that in many cases this makes no sense, but it could be a way to explain Celebi’s gimmick where dozens of it from different times appear: One summons one other. Next turn, both summon one more each- Etcetera.

Can the Chronurgy Wizard’s Chronal Shift ability be used when a creature passes a saving throw with Legendary Resistance?

From Explorer’s Guide to Wildemount, the Chronurgy Wizard’s Chronal Shift ability says:

You can magically exert limited control over the flow of time around a creature. As a reaction, after you or a creature you can see within 30 feet of you makes an attack roll, an ability check, or a saving throw, you can force the creature to reroll. You make this decision after you see whether the roll succeeds or fails. The target must use the result of the second roll.

Using the adult red dragon as an example, Legendary Resistance reads:

If the dragon fails a saving throw, it can choose to succeed instead.

Specifically, here is the scenario:

  1. Wizard casts saving throw spell on Red Dragon
  2. Red Dragon rolls the saving throw and fails
  3. Red Dragon expends one use of legendary resistance to succeed on the saving throw
  4. Wizard uses their reaction to use Chronal Shift to force the dragon to reroll the saving throw
  5. Red Dragon rerolls the saving throw and fails
  6. Red Dragon expends a second use of legendary resistance to succeed the saving throw

In particular, is step 4 of this scenario a valid use of the Chronurgy Wizard’s Chronal Shift ability?

For transparency, this question is a rewrite of this closed question, having this meta post about its closure. In response, I made this meta post that is more generally concerned with re-asking questions that were closed per our dont guess the system policy. Please avoid any meta discussion on this post, instead relegating it to the relevant meta posts.