Is this houserule preventing effects from dropping creatures to below 1 HP if they make their save exploitable or broken?

Question

I'm playing with the idea of adding a new house-rule to my sandbox-style game.

The rule is as follows:

If you succeed on a saving throw against an effect, that effect cannot make you drop below 1 hp.

I am hoping this will eliminate situations where an injured player rolls a 20 against a Dragon's breath weapon and then just goes down anyway because the half-damage eliminates them. In more extreme situations, it makes it so you don't instantly die with no chance if you anger a creature too powerful to defeat because the half damage might instantly kill you.

I also hope it encourages tactics both for monsters and players when dealing with a group of weaker enemies. According to the design principles, a large group of weaker creatures should remain a credible threat, but when a lightning bolt 100% takes out a whole line of them, regardless of their rolls or their cover (which is supposed to protect you from just that spell) that just isn't true anymore. With this rule, Goblins behind cover or who have advantage on the roll actually have a chance of surviving (with 1 hp, but at least they'll remain a threat). It will make these spells potent but not certain death.

However, I'd like to hear if anyone has tried this rule before, or sees any situations where this would be exploitable, broken, or "not fun".

Answer 1

This is going to be a poor idea

As other answers point out, this is going to make save-targetting spells significantly weaker, but there's also another problem you might not have thought about.

Being at 1 HP is more dangerous than being downed against big threats

This is going to leave a lot of players in combat running around with exactly 1 HP, which is prime instant-death territory. Most monsters are perfectly okay with letting a character make death saving throws to stabilize themselves, but they're not quite so okay with being stabbed in the back. (citation needed). Simply put, while downed, you are not a threat. When you're still standing at 1 HP, you're a threat and need to be taken out.

Example:

Bob the Dragon does his breath attack on Billy. Billy has a max HP of 35. The dragon deals 60 damage, but Billy succeeded on his save, so he only takes 30. That's still enough to down Billy who already took a beating from a Goblin earlier, but instead of going down, he's now at 1 HP.

That won't do, so the next turn Bob swipes at him and gets a crit. He deals 38 damage in one hit, enough to instantly kill Billy.

This will be even more obvious at lower levels, where succeeding your save against a spell might leave you standing at 1 HP next to an ogre who can one-shot kill you now even without a crit.

Answer 2

It'll significantly weaken save-targeting spells

The difference between zero hit points and one hit point is huge, far greater than the difference between one and two hit points. For every monster that survives with one hit point, your PCs need to hit it with a normal attack (or gamble again with a save-able spell) to kill it, and before one of your PCs succeeds, the enemies will fight back with full-powered attacks. You'll be facing longer combats, especially when fighting monsters who have poor HP but high AC (at low levels, hobgoblins are a typical example).

It's noteworthy that this change introduces new weirdness of its own: characters at 1 hp not dying to a repeated casting of a powerful area-effect spell is, in my opinion, worse than cover or advantage not mattering.

Answer 3

This would make damaging spells even weaker on higher levels

A 11th level Fighter with Great Weapon Master can do more damage every round than a 13th level wizard once per day with Finger of Death.
On those levels Magic Resistance, Legendary saves, condition immunities and resistances to damage types are quite common, so casters are even further behind than they seem by the numbers.

What casters have left beside buffing their own party is being effective against larger groups of weaker monsters, and your house rule would take even that away from them.

Answer 4

This is not a complete answer, but I'm adding it anyway in the hopes that someone will add it into their more complete answer.

This rule, as written, makes a character at 1 HP immune to damage from save-based effects as long as they can keep saving. This is, at best, kinda ridiculous.

Consider adding a clause that says "If you have more than 1 HP" so that a character who has survived by virtue of this rule once doesn't get to survive AGAIN.

Answer 5

In addition to what others have said, I can see this being "unfun" because it takes away from the classes that get Evasion. This rule would give everyone a weird form of that class feature.

It is stronger than Evasion because:

• It applies against every type of saving throw.
• It doesn't use up a class feature.

It is weaker than Evasion because:

• Failed saves still cause full damage.
• Successful saves still cause a reduction in HP (unless at 1 HP already).

Also, it would also cause any spells that improve saving throws much more powerful.

Answer 6

I would suggest modifying the rule to, let's say: No damage if save exceeds DC + 5.

Otherwise, I see 2 problems:

• Shield Master feat becomes less powerful. With it, you can use a reaction to negate damage from dex save where you would have received only half damage.
• These spells would have a very different impact on whether the character has 1 or many HPs.

Alternatively, you could say that the damage on save must exceed characters constitution + remaining hp to get them to 0hp.

For example, our character has 4hp and +3 con bonus and gets hit with a spell for 10 total damage. He succeeds the save so he should only receive 5 damage. It is more than our remaining hp but less than remaining hp + con bonus (4+3=7) so character remains alive with 1hp. On the next hit, he again succeeds and again gets hit with 10/2 damage. This time, remaining hp + con bonus is 4, which is less than 5 so the character does fall unconscious.

This approach would be less OP, but zombies with undead resilience would feel cheated :D