Demontrumpets, as illuded to by the name, are not normal plants, but are plants who hold their origin in the Abyss. Perhaps brought by summoned demons, perhaps created by a dark god for some purpose, perhaps simple plants mutated by an artifact of great evil.
A large, ruby-red pepper, found in dry regions; much prized by alchemists and gourmands alike.
The PCs are walking along the road, when suddenly a bunch of bandits attacks. The player's dismiss it has just a random encounter, when they find an ornate ring on the leader, obviously out of place with the seemingly poor bandits, who could only afford cheap leather and weapons. This ring has a symbol on it, which, if researched, sets the PCs on a quest. And from then on, the players don't look at random encounters the same way...