Based on Sandy Petersens Cthulhu Mythos, this adventure is full of hyper brainy ancient species who oppose the PCs. It can be hard to have the enemies who are smarter than the players, or for that matter, than the DM himself!
Yig Snake Granddaddy is an amazing campaign in which evil serpent folk seek to bring back prehistoric times, complete with pterodactyls, dinosaurs, and other monstrous beings.
In Land Out of Time, the first act of four, your player characters adventure into the wilds of Yilan, a primeval wilderness infested with carnivorous slime molds, gigantic crocodiles, and other lost horrors. There they encounter an evil serpent wizard, who prepares for an evil ritual beyond belief.
Betrayed, marooned, and hunted by super-intelligent enemies, can the heroes even survive, yet alone prevail?