Blackpeat Mire

An old causeway of split logs crosses Blackpeat Mire, and every traveller trusts it because it is the only firm ground for miles. Mirecrown waits under the peat beside it. He was a marsh lord once, drowned with his scepter in his fist, and he still speaks the languages he knew in life. Fenlantern drifts the open water with a pale lure on its brow. Sloughback lies across the path itself, a mound of moss and peat that a tired party will happily stand on.

All three want the same thing: a traveller off the logs and held fast in black water. Fenlantern starts it. Its Led Astray pulls one creature toward the lure, even into deep water, and its Marsh-Light strips away any hiding in the bright glow. Sloughback stays still under the feet of the rear guard until someone stops on its back. Mirecrown stays submerged, using Still Waters Run Deep to hide, and rises only when the party has split.

The causeway lies because the mire built it to lie. Half the logs float on the backs of things that are waiting. The front walker follows the light. Behind them, the back walker steps onto the hummock, and now the party is two groups with nobody on solid ground.

Every one of these monsters hits harder against a restrained target. Sinking Feeling sinks anyone within 10 feet of Sloughback to the waist on a failed DC 14 Strength save. If someone wades clear, Sloughback answers with Nobody Leaves, a free Crush attack that drops their speed to 0 on a hit. The Mire Rises restrains everyone on the ground within 15 feet of Mirecrown on a failed DC 15 Strength save. Fenlantern's Bite then does an extra 2d6 piercing damage to anyone restrained or in water.

Call the Fen ties the three together. When Mirecrown sees a creature become restrained, one ally within 60 feet of that creature moves up to its speed toward it without provoking opportunity attacks. Drag Under finishes the job: 3d10 + 4 bludgeoning and 2d6 necrotic, and the target can't breathe until the restraint ends.