The Resonating Sentry-Arch
A high mountain canyon terminates in a smooth, curved semi-circular wall of dark stone. Flanking the approach are two towering pillars composed of stacked, rough-hewn stone blocks that pulse with a low, blue light. When approached, the atmosphere turns hostile, sealing the intruders within a localized cyclone of arcane energy.
The Resonating Sentry-Arch
Defenses
Detection
“The semi-circular wall is composed of polished basalt that reflects nothing. The pillars consist of seven rotating granite segments each, carved with jagged, nonsensical grooves. A faint blue luminescence thrums through the rock, vibrating the very marrow of those nearby.”
Standard Engagement
The hazard activates when a creature of Small size or larger enters the area between the pillars and the semi-circular wall.
On Initiative 20, the Screaming Gale forces all creatures in the area to make a DC 14 Strength saving throw or be pushed 10 feet toward the back wall and knocked prone. On Initiative 10, if the Heat Level is 1 or 2, the blue thrum shifts to a red glow, and the temperature rises to Extreme Heat. If the Heat Level is 3, the wall acts as a Wall of Fire.
The hazard resets to its blue, dormant state if no creatures are within the semi-circle for 1 hour, or if the 5 successes are achieved. If the fire is triggered, it persists for 10 minutes after all intruders have left or died.
Violent winds circle the area. Flight is impossible within the canyon semi-circle. Creatures attempting to fly are immediately forced to the ground. Additionally, the wind acts as a semi-solid barrier, blocking all forms of teleportation (including Misty Step and Fey Step) into or out of the area.
After the third failed attempt to rotate a stone, the wall erupts in flame. This functions as a Wall of Fire spell (DC 15 save) circling the interior of the semi-circle and pointing inward. It deals 5d8 fire damage to any creature starting its turn within 10 feet of the wall or passing through it.
Every time a successful stone rotation is made, the walls vibrate but remain blue. Every time a failure occurs, the blue thrum shifts more toward a vibrant, angry red.
Upon the 5th successful check, all heat immediately drains from the cavern. The air grows preternaturally still, and the semi-circular wall rumbles slowly into the ground, revealing the path forward.
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