Obscurium has 8-voice saw, pulse, supersaw and FM synthesis capabilities. It has a motion sequencer and automation abilities. You can create sequences by drawing, using modifiers, or employing the Super Obscure mode (which lets the software conjure something for you).
OK, enough basic feature description. This thing will make your brain leak out of your ears.
It says a lot about Obscurium that the most challenging thing to do is get it to play the melody you gave it. If you're not using a keyboard to play notes in real time, I would suggest creating a MIDI sequence with another synth and then giving the sequence to Obscurium to see what happens. And I assure you, it WILL be transformed. I still haven't gone through all 400 presets, mainly because what it does is both audibly and visually fascinating. Fans of Imogen Heap, Autechre and Tangerine Dream will feel right at home - you will experience otherworldly pads, fidgeting arpeggiations and unique percussive sequences. When you feel ready to explore further, you can design your own sequences on the tapestry-like interface, modifying 16 different aspects of the sound, confining it to specific modalities and morphing through variations of your creation via sequencing or real time manipulation.
YOU CAN LOAD OTHER VST SYNTHS INTO IT AND USE IT ON THEM.
Summary/TL; DR - If you purchase this (and you should), give yourself a couple of hours to explore it. You will be fascinated, transfixed, and filled with a childlike wonder you haven't known in years.
It's not very often that you open a VST, play with it for several hours, and yet still fail to understand how it operates. Let's just say that Obscurium is so feature-packed that it's difficult to know what the hell is going on with it. Forget standard GUIs - this one relies on you drawing parameter changes on a sci-fi interface. Practically everything can modulate everything else. Pretty soon the screen is undulating with wave-like oscillations and morphing between sounds. The hardest thing to get out of Obscurium is a straight bass or lead sound. It's not really 'for' that, though. It's for stumbling upon really unusual and quirky stepped polyrhythms, or chord sequences you'd never normally think of, or cyber drum loops, or complicated evolving pads.
A bit like Sonic Charges' Synplant - when you've run out of inspiration, this might be one to turn to! It's best if you just throw caution to the wind and stat turning knobs. Don't worry too much about how you might have got there.