need help determining trap CR

[mtijn]

Hi, I have trouble determining the CR for a custom-made trap and was hoping anyone here would be able to assist. The campaign is a D&D3.5 campaign set in Forgotten Realms. My players have ventured into tunnels and caves in a volcano. One of the caves is the setting for my custom-made trap. The visibility is poor due to extreme heat (and shimmering). I don't know if this should affect the trap's CR.. Anyway, 200ft opposite the entrance is the exit. In the exit stands my players' nemesis. When the players have ventured one quarter into the cave he pulls a lever hidden in the wall next to him which sets off the trap. Long strips of the floor that span the entire length of the cave will start to collapse from entrance to exit, leaving only a few narrow (2ft) strips of floor left that arch from entrance-side to exit-side of the cave. Now because the floor collapses within 2 rounds (so not instantaneously) I will allow the players a reflex save of DC15 to escape sudden death. Anyone failing the reflex save will end up in the river of lava below that is the source of the extreme heat in this cave. Naturally this results in immediate and irreversible death. Those who succeeded on their reflex save will have to endure ranged attacks and darkness spells by their nemesis who watches the scene unfold from his position at the exit. This kind of trap isn't exactly described in the DMG so I'm struggling to find the correct CR.. help wanted, please!

[supermonkeyjoe]

Well seeing a a wail of the banshee trap is CR 10 and that offers a DC23 fortitude save or death, I'd say your trap would be around CR9ish, adding that CR to the villain would calculate the Encounter Level.

Just out of interest what level are your PCs? This could either be trivialised with the right spells and abilities or be guaranteed death for everyone.

[mtijn]

They are lvl 3. Maybe I better replace the lava river with something less deadly? That or I'll lower the DC for the reflex save to 10; by the time the trap kicks in the party will have ample time to react anyway, enough to account for a lower reflex save DC. I'll also add an extra check for saving nearby fellow party members.

[Arcanist]

I was going to start a new thread for this, but since you decided to make a thread about traps I matter as well throw my lot into it as well.


The Book of Vile Darkness briefly touches the subject of booby-trapped armor, but I'm curious if anyone else has given it any thoughts.

My personal favorite being the Glyph of Warding on the Backpack trap since it can also be planted on a Bag of Holding or a Handy Haversack or you use to carry your stuff around. I'm also curious if you can trap your armor with a self-setting boon trap.

ALL OF THESE WILL BE ANSWERED! Not by me, but I'm sure someone knows enough about traps to help me out here!

[supermonkeyjoe]

High lethality is fine so long as you give them a few chances to get out of it, 1 round to react as the floor starts to crumble, a reflex save to avoid falling and a reflex save to grab the edge should do, especially if there are party members around to grab hold of them.

Bear in mind that if the heat haze is causing the PCs to have a miss chance their nemesis should have a miss chance to hit them too, run well I could see this being a really fun encounter. Just be prepared for someone to get a string of natural 1s and take a lava bath.

[mtijn]

so with the DC lowered to 10 and the addition of 1 round to react and an extra reflex save, what would the new DC of the trap be? PS, I set the Search and Disable Device DC for this trap to 30 because it is a stonework trap initially constructed by highly skilful dwarves.