Earlier post I did on this subject years ago on the 339 boards
http://community.wizards.com/go/thread/view/75882/25907977/Sage_of_the_Six_PathsQuick Summary
Nightmares get Etherealness and Astral Projection as SU abilities
at will. Nightmares as long as they are touching their "allies" can transport themselves as well as their allies when they use the Etherealness ability.
If I remember correctly, when you use Polymorph Any Object on someone they retain their SU abilities. You effectively polymorph any object a nightmare to become your half zetsu body.
That combine with readied actions and you can easily simulate Tobi. Use the plane shift spell/power to attack
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A Vestigial Twin(5 LA, DMG2) simulates Zetsu nicely as well
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You can also do the same effect with psionics (but you blow through pp), using synchronicity to convert other actions into standard actions, (schism + synchronicity means 2 standard actions a round, use magic items to convert your swift action into a third synchronicity action.)
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1 Level of Ghost Savage Progression, combine with Ghostly Grasp, Ring of Manifestation (you keep ring on to appear human, take it off in battle), and the Human Heritage feat can also simulate tobi but he is still targetable by anything that can hit a ghost.