Thomas Markov’s answer does a good job of showing the probabilities, but doesn’t really explain the ‘why’.
To actually understand this, you have to understand how the normal advantage/disadvantage rules work.
Rolling 1d20 has an equal chance of each value from 1-20 coming up. Rolling 2d20 produces a triangular probability curve with a peak at 21. Rolling ...
I tend to agree with the other answers and comments saying that allowing advantage and/or disadvantage to stack risks slowing down the gameplay.
Such mechanics can work in some systems and contexts — there are entire rules-light RPG systems whose core task resolution mechanic boils down to "list every narrative circumstance that could give your ...
Frame Challenge: Complicating the Advantage system is not desirable.
I'll quote from a post I made several years ago on What issues could arise with this Advantage/Disadvantage Variant?
One of the aims of the advantage/disadvantage system is to remove the payoff for "bonus-scrounging". It isn't desirable to have your players constantly trying to ...
With one source of disadvantage, it takes 6 sources of advantage to have the same chance at a natural 20 as a straight roll.
Using this short anydice program:
If we set advantage to 6 sources, and disadvantage to 1 source, our probaiblity of rolling a natural 20 is 5.72%:
I can't really say if this phenomenon is ...
The rules say:
Any character or monster that doesn’t notice a threat is surprised at the start of the encounter.
That means they are surprised if they do not notice any threat.
In the scenario you describe, PC2 has noticed a threat and therefore is not surprised.
You've asked how to handle the case where PC2 is not aware of a combatant. The thing you ...
Balancing a spell of this format well for all three of those classes isn't going to happen.
This spell as written is difficult to balance because certain of its features make it significantly more useful/powerful for some casters than others.
Warlock: Straight-up, it's not realistically possible to balance this for both Warlock and Sorc/Bard. Most warlocks ...
It is not uncommon for NPC stat blocks to be simplified, and omit some of the abilities that a PC of the same level and type would have. The DM has to decide how to treat this.
In my world, I run it that the NPCs (and monsters, where applicable) operate by the same rules as the PCs, whether that is to their advantage or not. If an NPC (or a monster with ...
There is an NPC in Tales from the Yawning Portal that uses the Acolyte stat block plus Turn Undead.
Specifically, the Sunless Citadel adventure from Yawning Portal contains an NPC named Erky Timbers. Erky's statblock totally identical to the Acolyte statblock, except for the addition of Channel Divinity: Turn Undead:
As an action, Erky may present his holy ...
Looking at the Players handbook we can see this section on the Ready action:
Sometimes you want to get the jump on a foe or wait for a particular circumstance >before you act. To do so, you can take the Ready action on your turn, which lets >you act using your reaction before the start of your next turn.
Now according to your scenario the ...
I tried this once
For what it's worth, I allowed this around the time this question was asked although I did not see the question itself until this week.
The party had five characters with racial darkvision (grey elf sorcerer, wood elf ranger, mountain dwarf druid, half-orc barbarian, half-elf wizard) and three without (human monk, human fighter, human ...