You bind a spell into the rock and soil, leaving it there until an opponent stumbles across it. At that time, the spell releases its energy.
When you cast an earthbound spell, you place it within a square adjacent to you. You must specify all effects, options, and other relevant variables when you cast the spell. The next creature to enter the warded square triggers the spell. If the spell affects an area, that square is the center of the area or the point at which the area begins. For a cone, line, or similar area, you must designate the direction in which the cone or line extends. An earthbound spell that does not affect an area targets the creature that triggered it. You cannot apply the Earthbound Spell metamagic feat to a spell with a range of personal. An earthbound spell remains in place for 1 hour or until it is triggered. A Search check (DC 25 + the spell’s level) reveals its presence, as does detect magic and similar abilities. A character with trapfi nding can make a Disable Device check (DC 25 + the spell’s level) to remove an earthbound spell (as if it is a magic trap). A dispel magic effect can also remove an earthbound spell, thus preventing it from functioning. An earthbound spell uses up a spell slot two levels higher than the spell’s actual level.