Hallucinatory terrain

From Ardrana

By means of the hallucinatory terrain spell, the wizard causes an illusion that hides the actual terrain within the area of effect. Thus, open fields or a road can be made to look like a swamp, hill, crevasse, or some other difficult or impassable terrain. A pond can be made to look like a grassy meadow, a precipice like a gentle slope, or a rock-strewn gully like a wide and smooth road.

Note: This version of hallucinatory terrain originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.