So the PCs are in a dungeon and will be encountering the following trap:
Description: 9-0) Chamber of Echoes As you ascend the stairs to the penultimate floor, the sound of the dancing wind becomes clearer as the blue flames dance in the feint breeze. Once again the design of the embossments has changed; these appear to depict a swirling storm with the flame as the eye. As you reach the top you discover that the entire floor appears to be a single chamber with a multitude of columns rising from floor to ceiling. The wind from the air holes can be clearly felt and heard as though it was passing through wind chimes; the notes and pitch intermittently changing with the strength of the wind. The light on this floor bounces off the columns and casts innumerable shadows throughout. The ceiling of this floor does not have the exposed trusses like the other floors; instead it’s composed of many shallow domes with the lighting recesses at the points where the domes meet.
Mechanics:
• The columns are all covered in runes and glyphs which are arranged in various wave patterns; the top of the columns have openings that allow the passage of the air through them. The columns radiate strong evocation magic. Studying the markings on the columns for 10 minutes and succeeding at a DC 25 Kn: Arcana check will reveal the following:
o The patterns can be discerned to represent both wave cancellation and amplification effects.
o The patterns are interconnected and powered by the ley line; defacing any of the runes or glyphs will cause the chamber’s magic to become unstable. The chamber’s magic will short-circuit for 5 rounds; each character in the chamber must make DC 25 reflex save every time they move between columns (except for the defaced one) or be struck by a field.
• Observing the chamber and making a DC 35 perception check allows a PC to notice feint shimmering occurring intermittently between the columns. Further observation and a DC 15 Perform check allows the character to notice that the shimmering occurs whenever the note a column emanates changes.
• In order to safely pass between columns a character playing a wind instrument must match the proper note to phase cancel the note emanated by the columns. This requires a DC 15 perform check. Due to the notes changing due to the changes in wind strength and direction, even if the correct note is sounded there’s a 25% chance each round that the required note changes and the field returns. There’s a 5% chance the note changes to the opposite phase, which increases the damage by 1.5 until the performer changes notes. If the performer plays the correct note in order to step between the columns, there’s only a 10% chance they will be caught in a note change.
• A character who spends 4 consecutive hours in the chamber and makes 16 DC 20 perform checks can discern a pattern of the notes and then play the correct note in anticipation of note changes.
• A character caught between columns when a field forms can make a DC 25 reflex save to dodge of the way. Anyone struck by a field must make a DC 25 fortitude save or take 30d6 sonic damage. A successful save reduces the damage to 5d6. Anyone killed by this damage is turned to dust as if affected by a disintegrate spell.
• Because the power of the chamber is being fed by the tower’s ley line, dispel magic has no effect on any of the columns. A mage’s disjunction centered on the center column will deactivate the chamber until it’s reactivated from the nexus.
• At the other end of the chamber is the door to the stairs leading up to the top floor. The door can be opened by a knock spell.
Since this trap falls outside of the guidelines of the trap construction rules I've had to take a stab at evaluating it; right now I've got this as a CR 16 trap. Does that seem reasonable? Should it be less or more?
There's a lot to dissect here, but ultimately it's got two components - damage and disabling. It's ultimately boils down to being a disintegrate effect, so that's 1+6 (7) or 1+(30d6/10) (12). Since 12 is higher, we use that. Automatic reset, so 13. The disable/avoid is fairly complicated but it doesn't line up with the guidelines, so probably adding 2 or 3. That gives us CR 15 or 16.
On the other hand, it looks a lot like the Empowered Disintegrate Trap (CR 16) mentioned in the Environment chapter of the CRB. It's got automatic reset, so that adds 1 to the CR for 17. If you think the disabling and avoidance is less difficult than 33 Perception/Disable Device and True Seeing you could lower the DC by 1 or 2. If you think it's harder you could increase the DC. I personally think it's easier to detect and so easier to prepare for, so I'd peg it at the 16 you said.
@Scrapper - Whoa, good catch on the Silence spell part. I'll have to make an adjustment because I don't want the trap to be defeated by a 2nd level spell (or to be precise, the Wizard who created the trap was smart enough that he wouldn't have let such an obvious loophole go unaddressed).
@Berinor - I forgot about any Disable DC since the group doesn't have a rogue. I'll have to think about that.
The PCs do have some knowledge of the trap they obtained from an NPC lower in the tower. They know that the trap has a disintegration effect and that - according to the NPC, who they have reason to distrust - it can be apparently bypassed by playing a flute.
Does your party have a bard or flutist? Or even a flute? Or a way to make a flute?
At level 16 to 18, PCs can just Quicken Dim Door across the room....
Does your party have a bard or flutist? Or even a flute? Or a way to make a flute?
At level 16 to 18, PCs can just Quicken Dim Door across the room....
Teleportation is blocked in this room (and the floor above it), so that's taken care of. They don't have a bard but they can get a flute.