Tried out some suggestions last night. They went into a swamp looking for Lotus. I used rules supplements from Wildescape. They encounterd Swamp gas, disease, flies, leaches, stinging vermin. Were attacked by a large spider, and threatened by a jaguar. Slept on a miserable patch of dry ground. The climax, in addition to battleing the swamp demon (they all suffered grevously, they failed to defeat it, but did get the lotus), they had to deal with quicksand. The most tense-exciting moments were when one character was drowning in quicksand, he had 0 FP and another character braved the swamp demon, expended all his FP and rescued him, at the last possible moment - as the first character would have drowned then.
Thanks for the suggestions.