So you want to get that other-worldly, just arriving from the 5th dimension sound on a vocal track? Try a Reversed Reverb:

• Duplicate the track in question.
• Slice one of the vocal phrases on the new track into a separate region.
• Isolate it (remove all other region data from before and after)
• Note where the start and end points are. (this will be important later)
• Select it.
• Use the audiosuite reverse tool to reverse it.
• Now select the region and an amount about the same size after the region.Click here for a photo of the selection
• Use an audiosuite reverb (for this example, I’m using D-Verb’s Room2 on medium setting) on the selection. (you may have to do this a couple of times to get it to sound the way you want it to).
• Now reverse it again.
• Move the region back so that it’s end time is the same as it’s original end time from above (you noted it, didn’t you?) Shift+drag will snap the end time to the grid.Click here for a photo of the alignment
• Mix with the original.
• Listen.

Of course, you will need to tweak the settings to taste, but those are the basics.