The Void Lords clearly pooled their energies together to make these things and had Death Magic(at least in Yogg-Saron’s case) and Fel Magic(at least from what Y’Shaarj’s Hearthstone Picture shows) thrown in by the Nathrezim for good measure.
End result: Gods born of Death and Fel mixed with Void created by the Nathrezim & Void Lords take over the Void and ultimately imprison the Void Lords’ successor Xal’atath.
The Voidstorm is the last remnant of the Cosmic Void now that the Black Empire is in charge.
N’Zoth of course made the mistake of being in his own Realm when the Forge of Origination Re-Originated it into a Copy of the Emerald Dream infused with the Light of Azerite(Anduin notes that Azerite is similar to Beledar’s Crystals I should remind all of you) having his own mind being at the center of the beam.
N’Zoth the weakest of the Old Gods(still stronger than Dimensius considering his biggest tentacles are stronger than Dimensius’s full-powered Gamma Bursts in his own Realm which we can tank unlike N’Zoth’s largest Tentacles) is gone and had his Realm and Mind converted into a Light-Infused Copy of the Emerald Dream. The other Old Gods running the Void are probably laughing at his unfortunate fate.
In terms of power levels from weakest to strongest: individual Conclave of Wind Members → Thunderaan → Loken → Summoned Ragnaros → Thorim → Al’Akir → Ragnaros → C’thun’s Released Mind(the N’Zoth Raid made it clear what we face are the Gods’ Minds not their Bodies) → Yogg-Saron’s Shackled Mind → Ra-Den → Garrosh → Lei Shen → Deathwing → Aggramar in Titanforged Body → Argus’s World Soul → Denathrius → Sylvanas → Zovaal → Dimensius → N’Zoth → C’thun → Yogg-Saron → Y’Shaarj → Titans in Planetary bodies → Aggramar in Planetary Body → Sargeras in Planetary Body