Classicly

We had been heading toward a flat mountain wall that rose abruptly from the desert about a mile from the ship when—from nowhere—the creature appeared, towering above the desert like a dinosaur dropped from the skies.

But no dinosaur ever looked like this one. Sixty feet high, its skin a loathsome gray-green quivering jelly with thick hairy cilia projecting, its vat-like mouth gaping toothily, its cold, hard eyes flicking back and forth, searching for us as we flattened ourselves out of sight, it was an utterly ghastly being. Evolution had gone wild on this planet.