Question about fairness in a unique encounter.

So, in your scenario fairness is having characters that can NEVER miss? 

Nope that is a wrong interpretation.   Having a great skill bonus should not be negated 5% of the time, but that is not the to say they can't fail  either.  Rolling a 1 should not be the sole roll, there should be another roll or 2 (not necessarily a d20) that needs to fail as well.

Quote from Character77006 >>

rolled a Nat 20 which, in my game, negates the damage entirely

 

I feel this is problem number 1 which snowballs the other issues.  Rolling a 1 or a 20 is 10% of the potential rolls.  That should not mean an automatic anything.  Giving a 5% chance for a guaranteed hit/save is not always a decent choice like rolling a 1 should never be a guaranteed miss.  I had a character with a +21 and that 5% chance of a miss negates a great bonus.

DnD doesn't have many rules about special things happening on a 1 or a 20, except when it comes to attack rolls. For attack rolls, a 20 on the die always hits and a 1 always misses. I think that rule makes sense, because you should only be rolling dice if there's a meaningful chance of success or failure. You can have a +30 to your attack, but if you land a 1, it's still going to miss.

In the OP's scenario, I might have allowed the Rogue to use their Nat 20 to help the Druid, allowing advantage on the saving throw.

Anything outside of Ancient Dragons or Arch-Devils or Demon Lords will be an automatic hit, even if the character has disadvantage. To assume any warrior is so perfect that they can never miss or stumble in a fight is the definition of unfair. Now, if you play just for the mathematical precision of the constructed game, fair isn't a concept to be concerned with, I have a couple of players who would like to play that way sometimes. If you're more into the role play, no one is perfect.

Regarding the OP's question, I think you were completely fair. Your rogue rolled a nat 20, which is as fair a time for them to ask for something special as it ever would be. You told them the consequence before they committed, so you didn't blindside them. They made the decision to jump in front of the spell, and you resolved the spell fairly.

What this did was create an epic moment, which is perfect for a boss fight.

Regarding whether the twinned disintegrate was too much, it depends on the context. "We're going to fight the biggest baddest lich in the world, and he's the most powerful wizard who ever unlived", damn well expect some spell shenanigans. If it was "We're going to kill the huge bear that lives in the forest", and the bear starts twinning 9th level spells, the foreshadowing has gone awry, and they weren't prepared!

Fair is about whether they made a decision with the right information.

Quote from Stabbey_TC >>

Quote from Character77006 >>

rolled a Nat 20 which, in my game, negates the damage entirely

 

I feel this is problem number 1 which snowballs the other issues.  Rolling a 1 or a 20 is 10% of the potential rolls.  That should not mean an automatic anything.  Giving a 5% chance for a guaranteed hit/save is not always a decent choice like rolling a 1 should never be a guaranteed miss.  I had a character with a +21 and that 5% chance of a miss negates a great bonus.

 

DnD doesn't have many rules about special things happening on a 1 or a 20, except when it comes to attack rolls. For attack rolls, a 20 on the die always hits and a 1 always misses. I think that rule makes sense, because you should only be rolling dice if there's a meaningful chance of success or failure. You can have a +30 to your attack, but if you land a 1, it's still going to miss.

 

In the OP's scenario, I might have allowed the Rogue to use their Nat 20 to help the Druid, allowing advantage on the saving throw.

Quote from Stabbey_TC >>

Quote from Character77006 >>

rolled a Nat 20 which, in my game, negates the damage entirely

 

I feel this is problem number 1 which snowballs the other issues.  Rolling a 1 or a 20 is 10% of the potential rolls.  That should not mean an automatic anything.  Giving a 5% chance for a guaranteed hit/save is not always a decent choice like rolling a 1 should never be a guaranteed miss.  I had a character with a +21 and that 5% chance of a miss negates a great bonus.

 

DnD doesn't have many rules about special things happening on a 1 or a 20, except when it comes to attack rolls. For attack rolls, a 20 on the die always hits and a 1 always misses. I think that rule makes sense, because you should only be rolling dice if there's a meaningful chance of success or failure. You can have a +30 to your attack, but if you land a 1, it's still going to miss.

 

In the OP's scenario, I might have allowed the Rogue to use their Nat 20 to help the Druid, allowing advantage on the saving throw.

Where in the 2025 rules (I only have that) does it say a 1 is always a miss?

Quote from Character77006 >>

 

Where in the 2025 rules (I only have that) does it say a 1 is always a miss?

Chapter 1

Thank you.