D&D 5E Converting traps to 5e

[Tormyr]

At first I hoped that the conversion guides would be "Here is how to convert your earlier version adventure to 5e." Now I am starting to realize that the big 3 books already have most of that information. I had been wondering about converting traps from my 3.5 AP, but now I think there is actually enough information about it.

Apologies for the long windedness of this. Since there have been a few threads talking about the DMG and conversion guides, I am interested in a bit of input.

As an example in the 3.5 AP, the party is about level 7 and they encounter the following CR4 trap:Wide Spiked Pit Trap: CR 4; mechanical; location trigger; no reset; DC 20 Reflex save avoids; 40 ft. deep (4d6 fall); pit spikes (Atk +10 melee, 1d4 spikes per target for 1d4+5 each); Search DC 20; Disable Device DC 20.If I take the CR4 to mean a 5e Dangerous trap of CR 4, then it has the following stuff from the tables:

Save DC 12-15, Attack Bonus 6-8, damage 11 (2d10).But looking at how damage scales, in the trap table, 2d10 is going to be too low for a trap that has a 40 foot fall. Since the damage ranges from 1d10 to 24d10, it may work well to use as many d10s for damage as the CR of the trap. So this one would do So the 40 ft. 4d6 fall damage averages 14 instead of 11. I could ignore the fall damage in the calculations. 1d4 spikes per target would average 6 if they all did 1d4 damage. 1d4+1 damage each would bring it to 10 if they all hit for average damage. So how does this look?

1. Wide Spiked Pit Trap: CR 4; mechanical; location trigger; no reset; DC 14 Dexterity save avoids; 40 ft. deep (4d6 fall); pit spikes (Atk +7 melee, 1d4 spikes per target for 1d4+1 each); Search DC 14; Disable DC 14.

One difficulty I have with this is that the Rogue/Monk in my group has a passive perception of 19 because of expertise. I realize that perception does not always find a hidden trap.

Also, one thing that has always struck me as odd about the tables is that a Setback trap for high level PCs only has a DC of 10-11. So for conversion purposes I wonder if it would work better to have everything be on a scale. from CR1 to CR20, the Save DC ranges from 10 to 20, the attack bonus ranges from +3 to +12, and the damage ranges from 1d10 to 24d10. For a CR4 trap the values would round to Save DC 12, Attack Bonus 4 and damage 27 (5d10). Assuming all spikes hit (which is what monster calculation assumes) this, a converted CR4 trap would look like:

2. Wide Spiked Pit Trap: CR 4; mechanical; location trigger; no reset; DC 12 Dexterity save avoids; 40 ft. deep 14 (4d6 fall); pit spikes (+4 to hit, 1d4 spikes per target for 1d4+1 each); Search DC 12; Disable DC 12.The saves and attack bonus are fairly low on this, but the damage fits better.

Another way could be to have the damage on the sliding scale of 1d10 to 24d10 for CR1 to CR20, and use the resulting damage combined with the expected level of the party to determine whether the trap is a setback, dangerous, or deadly for the party. A trap that does 5d10 damage for a 7th level party would be dangerous, so the DC would be 12, 13, 14 or 15, and the attack bonus would be 6, 7, or 8. Since CR4 is near the beginning of the range, DC could be 12 and Attack Bonus could be 6.

3. Wide Spiked Pit Trap: CR 4; mechanical; location trigger; no reset; DC 12 Dexterity save avoids; 40 ft. deep 14 (4d6 fall); pit spikes (+6 to hit, 1d4 spikes per target for 1d4+1 each); Search DC 12; Disable DC 12.

I realize this is long, and I am probably over analyzing this, but I am interested in coming up with a straightforward formula that would handle the majority of trap conversions.So do you like 1, 2, or 3 the best, or do you have a different idea?

EDIT: Darn Quick Post stripping all the new line breaks.

 

[I'm A Banana]

If I take the CR4 to mean a 5e Dangerous trap of CR 4, then it has the following stuff from the tables:Save DC 12-15, Attack Bonus 6-8, damage 11 (2d10).

Reasonable starting point.

But looking at how damage scales, in the trap table, 2d10 is going to be too low for a trap that has a 40 foot fall. Since the damage ranges from 1d10 to 24d10, it may work well to use as many d10s for damage as the CR of the trap. So this one would do So the 40 ft. 4d6 fall damage averages 14 instead of 11. I could ignore the fall damage in the calculations. 1d4 spikes per target would average 6 if they all did 1d4 damage. 1d4+1 damage each would bring it to 10 if they all hit for average damage.

I think you're getting too caught up on technicalities.

The exact depth and damage isn't as relevant as the function of the trap. In 3e, a CR 4 trap vs. a level 7 party would function more as a level 7 "setback" or "dangerous" trap. So maybe maybe just simplify: it's a spiked pit trap that has the overall effect of dealing 4d10 damage to anything that falls in it. If you wanted to separate the falling and the spikes, have the fall deal 4d6 damage (40 ft.) and the spikes deal 1d10+3 damage to get roughly the same average "dangerous" damage. It'd be a pit that is dangerous for a level 7 party to encounter. Since your party isn't 4th level, it doesn't matter what it would be at 4th level. Don't worry about preserving the original's CR, just preserve the original's intent: it was a trap that would hamper the party, but not kill them, when they were 7th level.

 

[Warmaster Horus]

Use the guidelines as far as you want, but keep it simple. If it kills someone, well it was a trap, you know...

 

[Tormyr]

I need to go reread how the 5e DMG does the new spiked pit trap.

 

[Tormyr]

Reasonable starting point.



I think you're getting too caught up on technicalities.

The exact depth and damage isn't as relevant as the function of the trap. In 3e, a CR 4 trap vs. a level 7 party would function more as a level 7 "setback" or "dangerous" trap. So maybe maybe just simplify: it's a spiked pit trap that has the overall effect of dealing 4d10 damage to anything that falls in it. If you wanted to separate the falling and the spikes, have the fall deal 4d6 damage (40 ft.) and the spikes deal 1d10+3 damage to get roughly the same average "dangerous" damage. It'd be a pit that is dangerous for a level 7 party to encounter. Since your party isn't 4th level, it doesn't matter what it would be at 4th level. Don't worry about preserving the original's CR, just preserve the original's intent: it was a trap that would hamper the party, but not kill them, when they were 7th level.

Normally I would be worried more about intent, but because there is quite a bit to convert, it is easier to mindlessly apply some sort of formula rather than think about what each trap is going to do. Plus in this case I wanted to at least separate the damage types. 27 (5d10) average damage. 14 (4d6) bludgeoning from the fall. 13 (2d10 +2) piercing from the spikes would probably be closer to the 5e way of doing it.

 

[I'm A Banana]

Normally I would be worried more about intent, but because there is quite a bit to convert, it is easier to mindlessly apply some sort of formula rather than think about what each trap is going to do. Plus in this case I wanted to at least separate the damage types. 27 (5d10) average damage. 14 (4d6) bludgeoning from the fall. 13 (2d10 +2) piercing from the spikes would probably be closer to the 5e way of doing it.

Perhaps a more expedient rule of thumb, then:

1) What party level is this dungeon intended to be run at? (use that character level on the 5e charts)
2) Is this trap supposed to kill someone? (if definitely yes, make it deadly; if definitely know make it setback; if maybe, make it dangerous)
2a) To determine this, figure out if the trap goes with monsters or other traps in the same "day" (ie, the party isn't expected to heal between them). If so, setback or dangerous. If it stands on its own, deadly.