Tantra is a rhythmic multi-effect plug-in with a rich feature set and high quality processing modules. With Tantra you can get any kind of sound and turn it into a complex rhythmic progression, with lots of movements among the deep produced sound space.
This plugin is excellent for easily creating sound effects with just the click of a button. The presets it contains already demonstrate the power of this VST, and I'm sure you could go much farther. Has been very useful to me in creating unique pad synths and decimation chords, along with various other uses. It does have a huge interface though, which can present a problem when you running on a low resolution monitor (my monitor is 1680x1050 and it's takes up nearly the whole screen height-wise).