The Soul Staff is one of the possible three unique weapons crafted by Orthanc in SpellForce: The Order of Dawn.

I could make you a weapon you've never even dared to dream of, warrior. But for that I need material that is more precious than a kingdom.
Orthanc about his plans

Upon having completed the quest Soulstones it will be handed over to the Phoenix Bearer. It was made for mages with light weight and has some great benefits through the used souls.

The other two soul weapons