Source: Tome of Magic
You can cast a mystery without line of sight or line of effect to the target.
Prerequisite: Any two metashadow feats.
Benefit: Once per day, you can apply this feat to a mystery which enables it to affect a target even if you do not currently have line of sight or line of effect. The target must still be within the spell's maximum range, and you must have line of sight and line of effect within a number of rounds equal to your Intelligence modifier. The target gains a bonus on his save, if any, equal to the number of rounds since you had line of sight or effect. You cannot apply this feat to any mystery that requires a touch or ranged touch.
Casting a mystery with line of Shadow is a full-round action.
Special: You can take this feat up to four times. To take it second time, you must have five metashadow feats. To take it a third time, you must have eight metashadow feats. To take it a fourth time, you must have eleven metashadow feats.
Normal: You must have line of effect or line of sight to target a creature or object with a mystery or spell.