Stormbound, the ship rolls hard over to once side. All that is not strapped down is tossed violently overboard in a splash of freezing water.
There, on the horizon- a tower. Squat, it stands alone on a tiny island. However, it's the only land in sight, and any more of this ferocious storm will crush the boat to splinters.
Taking shelter within the ornate entryway of the squat tor, the party notes with interest that no signs of life break the silence of the stone tower. As they take another step forward, they realise why.
This is the fabled tower of Brenji, a rich merchant who wished none to share his enormous wealth. He constructed this tower to store his gold- trapped and ready for any potential thieves. But the ingenious pitfalls and scything walls are not the only dangers within the silent walls of the building. A guardian, left behind by Brenji, still stalks these very halls.
A rattling hiss echoes somewhere from below...
You find a patch of edible funghi. They taste well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick with pains, vomiting, all the fancy stuff. As a gift or good meal, it could be a cruel joke or to make sure the heroes spend their time focused on the mission. And the fine soup you had in the inn yesterday could have some in.
(Inspired through a real-world fungus. Was really used to cure alcoholism.)