So, while thinking on the recent Lucky/Portent question, something has come to my mind:
The Lucky Feat states
You can choose to spend one of your luck points after you roll the die, but before the outcome is determined.
When exactly is the outcome determined?
I can see how it is not determined in scenarios where there are still unkown variables in place, such as the Attack Bonus or AC from a monster the party is fighting against, or the DC of a challenge they have to overcome. But I don't see where I draw the line in some other scenarios.
Some examples of these scenarios:
- If you make an attack roll and roll a 20, the outcome is instantly determined - you hit. It doesn't matter the enemy's AC or the bonus you are going to apply, the outcome will be the same (as in 'it is already determined').
- If you are making a Death Saving throw, the instant you roll the outcome is determined. You either succeed or fail, without any bonus to apply. The DC is also known and fixed (10), so there is no unknown variable.
Even if the outcome is determined in the same moment you roll the die (i.e. "After you roll, before the outcome is determined" doesn't exist) it seems obviously intended that you can still use the Lucky feat. It wouldn't make much sense that you can't use Lucky to change an enemy's attack roll just because it was a Nat 20 (confirmed by Crawford) and Lucky can be used in Death Saving Throws.
As a bonus:
- For the DM, the outcome is determined the instant he sees the roll for (almost) everything. He even knows exactly the outcome (not only 'it hits', but 'how, when and where it hits'). Can a DM ever use an NPC with the Lucky feat?