The Seekers are led by Ravenous, and ultimately report all the way up to Annihilus. They are imbued with the Opposing Force, or "The Essence", which is the Negative Zone's version of the Power Cosmic.
For the Seekers and Ravenous, their bodies are the conduits of the power which actually resides in creatures called Currs. They tether themselves to the Currs to take advantage of the Opposing Force. If separated from their Currs or if the Currs are destroyed, regeneration is quick.