The homebrewed rule you had to make and why you had to make?
I'm interested in everyone's homebrewed RP rules or really any game rule you instituted and why!
I'll go first!
As a DM, I think I have a pretty common (maybe) homebrew rule of "If You Say It, Then That's What Happens". So in-game you saunter up to the big bad evil guy and in RL you snidely say, "I SPIT ON HIM." Well, there's no backing out now, I'm afraid. I think it helps give players a pause to really think about and engage with situations. Then occasionally they forget and act on impulse and shenanigans ensues.
My family has a lovely homebrew rule of winner cleans up. Keeps the winners humble and makes losing a little sweeter.
I have a rule called Cascade and it's been pretty popular for a long time.
Starting at the second level in 5e, whenever you roll new maximum hitpoints for your level, I roll against you as the DM. We take whoever has the higher number. This raises the average of getting a non-garbage result while keeping it random.
However! If we both roll the same number, then we keep that and roll the next lowest die type down from that, following the same rules as before, until the dice don't match again. When we no longer match, you take all those matching numbers and add them together, with your Con mod only added once. This makes for some hilarious results and the players get to enjoy a bit of free gambling for a big permanent prize. This is 'cascade'.
First Example: You roll a cleric's d8 hitdie for your level. You get a 5. I roll a 7. You take the 7 instead of the 5, adding your Con mod as normal, and that's it for the level. Not a bad result, but not a 'cascade'.
Second Example: You roll a cleric's d8 hitdie for your level. You get a 5. I roll a 5! Keep that handy. Now we both roll a d6, the next descending die type.
You roll a 3. If I roll a 3, we continue cascading, until we get down to a d2. Add all the matched numbers, add Con mod once, and there ya go. Crazy hitpoint boost for the level and the player is pretty happy.
Alternatively, if I rolled 4 or whatever, you'd take that 4, take the 5 from the previous roll, add Con mod once, and we're done. Still, some nice chunky hitpoints to gain.
Why did I make this?
Outside of being something of a mad scientist with D+D rules for fun, the Cascade homebrew offsets trash rolls. No barbarian in existence wants to roll a 1 for their new hitpoints. It's horrid. And we like rolling at our table. Chaos is always good. It adds excitement that doesn't exist through averaging hitpoints or taking a single crummy roll.
It's also amusing to have something like a Wizard with some modestly tanky hitpoints. Cascade protects squishy classes from deadly crits.
Also, because squishy classes have lower hitdie types, they have a better-than-average chance of getting a higher roll or a cascade roll than the tank, who still has the chance, but just less need for it.
We've been doing Cascade for at least a decade now and I've never heard complaints about it.
"So, who's feeling lucky? Roll dem beautiful hitpoints, sir."
OMG I love that! I've always felt hit points were done terrible and usually I just say max hit points. No one wants to end a fight after the second round cause they are squishy and I rolled well. But I love this idea way more! It feels fun and authentic cause dice are still thrown.
I also recently saw a rule around rolling 1s that I absolutely love! I play a lot of FATE, where a fail doesn't mean you don't succeed, just succeed at cost. I prefer this. But this person had their players roll to confirm combat 1s.
If you rolled a natural 1 (crit fail) then they had you roll another d20.
If the second roll was equal to or less than your level, then you just missed your attack. If you roll above your level then it's a true fumble.
The rationale was that lower-level adventurers were more likely to drop their weapons, whereas a seasoned level 20 fighter should almost never. A level 20 fighter is someone who is so skilled that even if they miss, they shouldn't be hurting anyone.
I love this rule for 5e combat.
@mianngu Interesting. What happens during true fumbles in that game? Just weapon drop?