D&D 5E Rules We Have Been Doing Wrong This Whole Time

[DND_Reborn]

Also that you roll 1d4 per magic missile, when in fact you only roll 1d4 (+1) and each missile does the same damage.

I've heard this before, but nothing in the spell description implies that IMO.

Anyway, to the OP as far as rules I've been doing wrong in 5E... there was something, I recall that, but once I learned I was mistaken, I haven't done it wrong since... so I've forgotten it at this point LOL!

 

[DND_Reborn]

It is not stated in the description of Magic Missiles, but in the section for Damage Rolls on page 196 in the PHB.
"If a spell or other effect deals damage to more than one target at the same time, roll the damage once for all of them". I believe it was Sage Advice that clarified it.

Ah, yeah, that would not apply to magic missile IMO, because each target is not taking the same base damage. IF magic missile was limited to one missile per target, then sure that would be an easy way to do it. But since I can send one missile to one creature, two missiles to a second, they aren't taking the same damage.

Now, something like burning hands, where each creature takes the base 3d6, it makes since to just roll once since I don't want to roll 3d6 three or more times, then make saves, and calculate half damage for each if necessary.

 

[Retreater]

I was informed in March that I had been doing Hit Dice during short rests wrong.
I had been doing it this way: declare how many Hit Dice you want to spend at the start of your short rest. At the end of the short rest, you heal Hit Dice plus your Con bonus. So a 3rd level fighter with a 16 Con spending all her Hit Dice would get 3d10+3.
The actual rule (as you probably already knew) is that the Hit Dice should give 3d10+9. And the fighter can spend 1d10+3 at a time at the end of the short rest until they are happy with the result or they run out of Hit Dice.
Oh well. I don't think it's broken my games or anything.

 

[DND_Reborn]

Anyway, to the OP as far as rules I've been doing wrong in 5E... there was something, I recall that, but once I learned I was mistaken, I haven't done it wrong since... so I've forgotten it at this point LOL!

I was informed in March that I had been doing Hit Dice during short rests wrong.

AHA! You nailed it!

But what I always forgot for HD during a short rest was to add your CON bonus to the die rolls!

Luckily, once that was brought to my attention, it wasn't an issue afterwards.

 

[Jer]

The actual rule (as you probably already knew) is that the Hit Dice should give 3d10+9. And the fighter can spend 1d10+3 at a time at the end of the short rest until they are happy with the result or they run out of Hit Dice.

Wait - have I been doing it wrong? I thought this was just how hit dice spending worked (that you spend them one at a time until you decide to stop) not just for fighters. Is that a special fighter ability that I've been giving to everyone?

 

[Mistwell]

I don't know what that is even a thing. "I rolled a 20. I seduce the dragon!" ugh.

The dragon child in our campaign will be happy to take this up with you when they come of age.

 

[Retreater]

Wait - have I been doing it wrong? I thought this was just how hit dice spending worked (that you spend them one at a time until you decide to stop) not just for fighters. Is that a special fighter ability that I've been giving to everyone?

Nah. I just used a fighter as an example. It works the same for all classes.

 

[pukunui]

I admit when I started playing, I got darkvision wrong as well, mostly because everyone else I was playing with did. Then I started running 5e, and my first adventure was Sunless Citadel, a tier 1 adventure with tons of DC 15 and 20 Perception checks. The players all had darkvision, and were planning to not use any light in the adventure.

On a whim, I looked up darkvision, realized how it worked, noted the disadvantage on Perception, and it didn't take long before someone started using dancing lights, much to the Rogue's annoyance.

I am running Dungeon of the Mad Mage, which is mostly unlit and the secret doors are all DC 20 to detect.

One of the players, who is playing a dwarf cleric/paladin and has a high Perception, took the Dungeon Delver feat thinking the +5 from advantage to his passive Perception would let him auto-detect all the secret doors … until I pointed out that since the party all has darkvision and doesn’t use any light, the disadvantage to Perception from the dim light would negate the advantage from the feat. So if he wants to be able to auto-detect all the secret doors, he’s going to need to start using a light source.

 

[James Gasik]

I am running Dungeon of the Mad Mage, which is mostly unlit and the secret doors are all DC 20 to detect.

One of the players, who is playing a dwarf cleric/paladin and has a high Perception, took the Dungeon Delver feat thinking the +5 from advantage to his passive Perception would let him auto-detect all the secret doors … until I pointed out that since the party all has darkvision and doesn’t use any light, the disadvantage to Perception from the dim light would negate the advantage from the feat. So if he wants to be able to auto-detect all the secret doors, he’s going to need to start using a light source.

I've run into people who hate darkvision, and even if you point out the disadvantage, they say "ah, that's no big deal". I don't know why, because from what I saw running Sunless Citadel, it absolutely is a big deal.

 

[Charlaquin]

The description is ambiguous.

And I’m pretty sure the Sage advised that you can do it either way.