Crossing the Blackwater Mire requires the party to complete a progress countdown (6). The route is unstable: hidden silt pockets, collapsing reed-mats, gas vents, and false channels.
PCs can use appropriate actions (navigation, survival, scouting, magic, teamwork) as agreed at the table.
On a successful roll, tick down the countdown by 1 (or more at GM discretion for especially clever play).
On a failure, the party still makes progress, but the GM triggers one Mire Hazard below or inflicts a cost (lost time, dampened supplies, attention drawn).

Spend a fear to have the ground give way beneath a PC (or their pack/animal). They must make an agility reaction roll.

On a failure: they sink hard. They can be hauled out, but: lose an item, ruin a supply (tinder/food/rope), or mark a stress.
On a success: they scramble free, but mark 1 stress from the strain and panic.

Spend a fear to let the mire’s chill seize a PC’s body—hands numb, breath shallow, joints stiff. They must make a presence or fortitude reaction roll (use what best fits your table’s fiction).

On a failure: mark 1 stress and they’re slowed (the next relevant roll suffers disadvantage / higher risk, per your table’s approach).
On a success: they push through, but lose time—tick the progress countdown down only if another PC takes the lead or they spend a resource (dry cloth, heat source, tonic).

Spend a fear to release a pocket of marsh gas at the worst moment (near flame, during a rescue, or while crossing reeds). A PC must make an agility reaction roll.

On a failure: flame gutters or flares—lose a light source, ruin a supply, or draw attention (the next adversary encounter starts closer/tenser). Mark a Stress.
On a success: they smother it or back away in time, but the fog briefly thins—revealing something watching (a hint, not necessarily a fight).

Spend a Fear to introduce a blinking lantern and a strapped pack on a post or half-sunk skiff.

It’s either a rescue (someone alive, trapped in silt) or bait set by a hunter that tracks sound and light.
If the party investigates carefully and succeeds, grant a Tier-1 reward (see below). If they rush, trigger Silt Suck immediately.

Spend a Fear to summon one or more adversaries from the list above. They appear very close—a ripple behind reeds, a silhouette in fog, footsteps on a hidden boardwalk. They may not attack immediately; they might demand a price, stalk the party, or force a choice.