Mirage Arcana (Illusion)
Level: Mage 6
Mana: 16. Long duration. Base Success: 75%.
  This spell is similar in effect to the 4th-level illusion hallucinatory terrain, but much improved and wider in scope. Like the improved illusion spells, it affects all natural and exceptional senses and can only be seen through with true seeing or similar magic. It affects a 60-foot radius rather than a 30-foot one. Most significantly, however, it allows the illusionist to conceal terrain as well as create it -- a river of magma could be made to look like a shallow stream, or a chasm could be concealed with the illusion of smooth floor. The concealed terrain is real, of course, and has its full normal effect if monsters (or the player character) are tricked into walking over it, though these effects are concealed from their perception.