Banshee's Symphony 18
Complex Magical Trap
Stealth: +30 (legendary)
Description: A magically contagious wail of the banshee spell is trapped in the larynx of an invisible, mummified elf.
Disable: Thievery DC 42 (master) to pierce the invisible larynx so precisely that the magic releases in a trickle before the trap activates, Thievery DC 44 (legendary) three times to deconstruct the larynx while the trap is active in such a way that it tears the spell apart, or spell DC 38 (9th level) to counteract the wail of the banshee before the trap activates
Trigger: Three or more living creatures remain within 100 feet of the trap for 6 seconds or longer Effect: The trap releases an arcane wail of the banshee (DC 40) with a 100-foot-radius emanation instead of 40 feet, targeting all living creatures in the area, and rolls initiative.
Reset: The trap ends when the trap is unable to make a creature scream (usually because no creature failed its save on the previous turn or because all creatures have critically succeeded in the past). It then resets over 24 hours, as a new scream builds up in the mummified larynx.