Class names and in-universe terms don't need to be the same
What, really, is a 'bard'? It's somebody who earns their living by entertaining people with music and song. This doesn't require any form of magic, a peasant with a lute and a good singing voice could still make a living as a bard, even though they have no levels in the bard class as a player would ...
A weapon is only a ranged weapon if it is listed as a simple/martial ranged weapon. Every such weapon also happens to have the Range property
Note that fifth edition defaults to Standard English when something is not defined in the rules; however, what a ranged weapon is, is defined. The section on "Weapon Properties" includes the following:
Every weapon ...
The Balance Implications would probably be minimal
In my experience as a DM for several different settings, the range of creatures that typically have resistance or immunity to Fire Damage is not meaningfully more or less powerful than the (comparably few) creatures that typically have resistance or immunity to Psychic damage, nor are they especially more ...
Yes, you can write it
You have learned thieves’ cant, a secret mix of dialect, jargon, and code that allows you to hide messages in seemingly normal conversation. It takes four times longer to convey such a message than it does to speak the same idea plainly.
In addition, you understand a set of secret signs and symbols used to convey short, simple ...
Sneak Attack only works against creatures
The Sneak Attack feature states:
Beginning at 1st level, you know how to strike subtly and exploit a foe’s distraction. Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.
You don’t ...
No, the poison's damage is not part of the attack and therefore not doubled
Death strike explictly states that the attack is doubled (emphasis mine):
. . . On a failed save, double the damage of your attack against the creature. (PHB, p. 97)
Damage from poison applied to a weapon has been clarified as being separate damage from the attack entirely, due ...
They would not fall, but flying speed would be reduced to 0
The Fly spell reads:
The target gains a flying speed of 60 feet for the Duration.
Since flying speed is a speed, This means that when speed is reduced to 0, flying speed is also reduced to 0. The rules on flying speeds being reduced to 0 read:
If a flying creature is knocked prone, has its ...
From the situation you present, there is nothing that makes me jump. A "rogue/thief" can be of any class. Now does "All the Rogue abilities" mean the bard had sneak attack, uncanny dodge, and other?
NPCs do not have to confirm to exactly the same rules as PCs, it depends how the npc was built.
Was the NPC interesting? If so, then roll with ...
Resistance and Immunity
Fire is the fourth (third if you exclude nonmagic weapon damage) most commonly resisted damage type as well as being second most common to be immune. Almost all fiends are resistant or immune, Fire elementals, Fire giants, and the list goes on. The only damage type less resisted than Psychic is Force (although Radiant has more ...
From the Sneak Attack feature (emphasis added):
you can deal an extra 1d6 damage to one creature you hit
Objects are not creatures, and so Sneak Attack does not work on objects. Unless your DM is lenient, of course.
A wand is not a ranged weapon. Ranged weapons are on the Weapons table in the equipment section. Wands are not, they are in the Adventuring Gear section. That means that a wand, by itself, is not a weapon.
Spells are also not weapons, so while you're making a ranged attack with a spell, it is not using a ranged weapon.
Per the feature description:
During your rogue training you learned thieves’ cant, a secret mix of dialect, jargon, and code that allows you to hide messages in seemingly normal conversation. Only another creature that knows thieves’ cant understands such messages. It takes four times longer to convey such a message than it does to speak the same idea ...
It just says it's an action, so it's just an action
The invocation just says that you have to take an action while in dim light to become invisible. As such, any bonus actions or movement that you make before using that action, does not prevent the action from happening (unless stated otherwise). So, you can move, and if you use cunning action then yes, you ...
If a Rogue uses his or her Master of Tactics feature to Help a spell-caster in the party, would it grant advantage on a spell attack?
Yes. A spell attack is an attack.
I guess this would only work if the other party member casts a spell that requires a spell attack against a creature, rather than the a spell that requires the creature to make a saving ...
As an additional bit of flavor to add to the answers so far, I have found this video by MonarchsFactory (Dael Kingsmill) quite inspirational for portraying Thieves' Cant in game. Of note, she goes into some detail about what "written" Thieves' Cant might look like. Not strictly official, but as the other answers note, a written version of Thieves' Cant is ...
The rules for rogues convey the ability to understand and speak in Thieves Cant AND:
In addition, you understand a set of secret signs and symbols used to convey short, simple messages, such as whether an area is dangerous or the territory of a thieves' guild, whether loot is nearby, or whether the people in an area are easy marks or will provide a safe ...
While holding this shield, you have advantage on initiative rolls and Wisdom (Perception) checks.
Ring of Truth Telling
While wearing this ring, you have advantage on Wisdom (Insight) checks to determine whether someone is lying to you.
Eyes of the Eagle
While wearing them, you have advantage on Wisdom (Perception) ...
You can move before or after your action
So, you can move some or all of your speed and then take your action to, in this case, become invisible.
You can take a bonus action when the criteria are met
The criteria for Cunning Action is "on each of your turns in combat". So, if you are in combat and it's your turn you can do this and then take your action ...
Dungeon Delver gives advantage on Wisdom (Perception) checks to find secret doors.
Lucky gives you an extra die on attack rolls, ability checks, or saving throws three times a day.
Magic Initiate would give you access to the Guidance cantrip (see below).
Enhance Ability: Owl's Wisdom (2nd level) will give you advantage on Wisdom checks for ...