Shadow Strike: Sorcerer/Wizard 5, Hexblade 4, Witch 5
School illusion (shadow)
Casting Time 1 standard action
Components V, S, M (a handful of sand)
Range close (25ft. +5ft./2 levels)
Effect quasi-real double and invisibility
Duration 1 round/level
Saving Throw Will negates; Spell Resistance yes
You simultaneously create a doppelganger from shadow substance while rendering yourself invisible. Your shadow double appears superimposed upon yourself and immediately charges a target you chose at the time of the casting of the spell. It will continue to attack this enemy, or the closest enemy if the original target is impossible to reach or slain. You may redirect its primary target as a move action. It only employs physical methods of attack.
Enemies who perceive the illusory nature of your double take only 20% damage from it, and treat its AC bonuses as 1/5 as large. Regardless their disbelief, the shadow double has as much health as you designate up to 1/5 your maximum. The shadow double attacks with all your skill(including enchancement, feat, and ability bonuses) and, to a believing adversary, strength. It does not however utilize any skills that you have access to on a limited basis, such as stunning fist. It wields your currently equipped item, or utilizes the most logical weapon you possess, including unarmed strikes. Items with temporary charges are duplicated in sight, but not in effect, including spellstoring weapons. Enchantments on yourself persist onto your double at the time of casting, except for invisibility. The shadow spills into sand if destroyed, dispelled, or the duration expires.
An enemy watching you cast this spell will believe that you are your double, until he receives reason to believe otherwise. Any enemy struck by the shadow may make a saving throw. Enemies with true seeing, see invisibility, or enemies that rely heavily on senses other than sight will not be fooled.
Upon the completion of this spell you receive the benefits of invisibility as per the spell, but for only 1 round/level.
Ended up being a bit longer than I intended. Obviously mainly benefits a Gish character (or a heavily buffed polymorphing character I guess). Too strong? Against a failed willsave increases your damage pretty enormously...
EDIT:miss type on the duration