Mastery of the Mists

 
Prerequisite(s): Knowledge (the Planes) 6+ ranks, Spellcraft 12+ ranks.
 
Benefit:: By learning of the intricate relationship between the Ethereal Plane and the Material Plane, you gain the ability to see and sometimes reach through the barrier between these two planes. As a move action, you can see ethereal creatures and objects as if you were under the effect of a see invisibility spell for 1 round. (This ability doesn't let you see other invisible creatures or objects.) When you cast a spell on the Material Plane, you can attempt a caster level check (DC 15 + spell level) to target an ethereal creature or object you can see as if it weren't ethereal. Spells without a target entry (such as fireball) can't benefit from this ability. No more than one ethereal creature or object can be targeted with a spell in this manner, and you can't target ethereal and material creatures or objects with the same spell when using this ability.
 
Source: Player's Guide to Eberron