D&D 5E Break this House Rule: Advantage(s) can stack

[TwoSix]

Basically, what it says in the topic. If I had a house rule that said the following:

"Every source of advantage gives you one advantage. Every source of disadvantage gives you one disadvantage. Advantages and disadvantages cancel. If you have any advantages left over, roll an extra d20 for every advantage and take the highest roll. If you have any disadvantages left over, roll an extra d20 for every disadvantage and take the lowest roll."

Are there any feats/spells/class features that would be totally broken (either unbalanced or unusable) with that house rule?

 

[Dausuul]

As a rule, even guaranteed success on a given roll is rarely going to make or break an adventure, so I don't think this will cause balance issues. The one thing I would be careful of is saving throws. It's very hard to impose disadvantage on saves in 5E, but it's not impossible, and stacking disadvantage on a key saving throw could be a game-changer. Other than that, it should be fine, balance-wise.

As I understand it, the main reason for not allowing advantage/disadvantage to stack was to cut down on bookkeeping. If you don't mind the slowdown in combat, stack away.

 

[Tony Vargas]

Basically, what it says in the topic. If I had a house rule that said the following:

"Every source of advantage gives you one advantage. Every source of disadvantage gives you one disadvantage. Advantages and disadvantages cancel. If you have any advantages left over, roll an extra d20 for every advantage and take the highest roll. If you have any disadvantages left over, roll an extra d20 for every disadvantage and take the lowest roll."

It'd get silly, I suppose, but also self-limiting, as the marginal impact of each additional die would decline.

More simply, you could figure "Net" adv/dis, that is, have multiple sources of Advantage & Disadvantage cancel, leaving you with net Advantage (whether x1 or x10) or Disadvantage, but just resolve that normally, with one extra die.

Either way, you'll have people stretching for more Advantage for themselves, more Disadvantage for the other side, with no upper limit, but with diminishing returns.

 

[CleverNickName]

As I understand it, the main reason for not allowing advantage/disadvantage to stack was to cut down on bookkeeping. If you don't mind the slowdown in combat, stack away.

This. The whole point to A/D was to avoid repeating the tedious bookkeeping of 3rd Edition, where it wasn't unusual to have a half-dozen different modifiers on nearly every single die roll. "Okay, I'm attacking. I have a +2 to Strength, another +1 for the Weapon Focus feat, +2 because I'm flanking, +1 from that bless spell, ...what do you mean I'm not flanking? Um, in that case I also take a five-foot step so I can be flanking again, so that's another +2...wait, did I already add that in? Let's start over. I have +2 to Strength..."

If you don't mind doing this all over again with dice instead of integers, and haggling with your DM and other players about how many Advantage dice and Disadvantage dice you get to roll at any given moment, I say go for it. But it's definitely not my jam.

It'd get silly, I suppose, but also self-limiting, as the marginal impact of each additional die would decline.

...

Either way, you'll have people stretching for more Advantage for themselves, more Disadvantage for the other side, with no upper limit, but with diminishing returns.

Also this. It would be better, IMO, to leave the A/D mechanic in place and either reduce the DC, or add a Inspiration or some other bonus for situational stuff.

"Make a Strength check with Advantage, and add a d4 to it" would be a lot easier to handle than "Make a Strength check with three Advantage dice."

 

[Blue]

I think that both in general it will be fine, and that those looking to abuse it will find a way. If your table is full of reasonable people, I see no problem. And each die is less effective in the boolean success/failure then than the one before it. Though still increasing odds (and crits).

If you have a table with people who are really going to look for the loophole or maximum use of this, going with the concept you purposefully introduced it so using it to it's fullest is allowed and encouraged, I'd beware.

With 60 seconds of thought I haven't come up with an abuse, but that is far from saying there are none. Maybe something with controlling lighting. Or Elven accuracy. Crit fishing. *shrug*

But again, if you play with a bunch of mature players, I'd have no qualms about putting it in. If something isn't cool, just talk with them.

 

[Xaelvaen]

Are there any feats/spells/class features that would be totally broken (either unbalanced or unusable) with that house rule?

To directly answer the question, I don't believe so - other than as @Dausuul mentioned with saves.

We use Net Advantage/Disadvantage as well, but each 'point' after the first just gives a stacking +1/-1. So if you have 3A and 2D, you just get Advantage. 5A and 1D, you get Advantage, with a +3 modifier on the roll. This -slightly- breaks Bounded Accuracy, but makes the extra Advantages feel worthy. We tried it with a player rolling 3 or more dice, but it just felt to really not be worth the bookkeeping.

 

[Dausuul]

Another option would be to play with the normal rules, but say that one advantage negates one disadvantage and vice versa; so if you have 3 sources of advantage, you can suffer 2 sources of disadvantage and still have advantage on the roll (instead of having it all cancel out and give you a normal roll, which is how it works by RAW).

That would do what I think you're trying to accomplish here, allowing multiple sources of advantage to make a difference, but it wouldn't lead to rolling big fistfuls of d20s and would limit the amount of bookkeeping. You don't need to count your sources of advantage unless you also have disadvantage.

 

[Esker]

Those with the -5/+10 feats would be all over trying to find stacking sources of advantage. Returns are still diminishing, but the lower the base chance of success, the more bang you get by adding dice.

For example, if you're trying to do something where you need a 9 or better to succeed (60% success w/o advantage), then the first instance of advantage buys you an extra 24% (like a +5), the second an additional 10% (+2), and the third only 4% (+1). But if you're starting out with a -5 penalty, you go from 35% success with no advantage, to an extra 23% with one source (about a +5), an extra 15% from two sources (+3), 10% more from the third source (+2), and still another 6% (+1) if you can get a 4th source.

Let's see, going for completely ridiculous here. How about a Kobold Barbarian 2 / Monk 5 / Shadow Sorc 4 / Rogue 2, taking GWM and Magic Initiate (Wizard)? Turn 1: Quicken Darkness (using SP to cast it as well so you can see through it) and Attack, using a weapon and Stunning Strike on the 1st attack and then shoving Prone on the 2nd. Owl Familiar gives help action. Turn 2: Cunning Action Hide, and Reckless Attack. The first attack on turn 2, assuming you have an ally within 5' of the target, has:

Advantage 1: Enemy is blinded from darkness
Advantage 2: Enemy is stunned from stunning strike
Advantage 3: Enemy is prone
Advantage 4: Familiar is helping
Advantage 5: You are hidden
Advantage 6: Attacking recklessly
Advantage 7: Pack tactics

for a total of 8 dice (and a better than 1 in 3 chance of a crit -- toss in 3 levels of Champion for the expanded crit range and your crit chance goes up to 57%...)

The second attack is down to 5 sources of advantage (a measly 6 dice), but you can repeat the stunning strike, and keep this up as long as they fail their CON saves and you have ki points. Now if you have a caster in the party with Faerie Fire and another with Web, which are both DEX saves and therefore automatic fails when the target is stunned...

Edit: Ah, crap, Kobolds are small so can't use heavy weapons without disadvantage.

 

[FrogReaver]

Basically, what it says in the topic. If I had a house rule that said the following:

"Every source of advantage gives you one advantage. Every source of disadvantage gives you one disadvantage. Advantages and disadvantages cancel. If you have any advantages left over, roll an extra d20 for every advantage and take the highest roll. If you have any disadvantages left over, roll an extra d20 for every disadvantage and take the lowest roll."

Are there any feats/spells/class features that would be totally broken (either unbalanced or unusable) with that house rule?

Crit Fishing.

Faerie Fire + Prone + Greater Invisibility + Oath of Vengance + Reckless attack feature would result in a very high crit chance. I'm not sure if it's enough to break anything but that's where my concern would lie.

 

[Esker]

Crit Fishing.

Faerie Fire + Prone + Greater Invisibility + Oath of Vengance + Reckless attack feature would result in a very high crit chance. I'm not sure if it's enough to break anything but that's where my concern would lie.

How are you going to get all of those things happening together? You need Barbarian 2 / Paladin 3, and then probably you want 7 sorcerer levels for smite slots and quickened Greater Invisibility. Then you still need an ally to cast Faerie Fire and another ally to take care of the prone part (preferably grappling them too so they stay prone). Then after all that you're getting about 50% more crits per attack than an Elven Accuracy build, and actually fewer crits per turn since you don't have extra attack. For something that requires a level 12 character and the coordination of two different allies, it doesn't seem broken to me.