Talk:Verdant Sphere/@comment-15720198-20191028032836

In addition to what Vann said, Kael'thas' Verdant Spheres were corrupted by the corruptive energies of the Sunwell after Kel'Thuzad had been brought back. Him, Rommath and Astalor used them to destroy the Sunwell by overcharging them, and then he collected them afterwards, and they had retained the corruptive power of the corrupted Sunwell.

Additionally, the WoWPedia Page states that not all Verdant Spheres are Fel Based, as Felo'Melorn in Legion gave Fire Mages three fire-based Verdant Spheres. It can be assumed that through this, a mage with enough power and need for additional foci through which to cast spells, can indeed create a Verdant Sphere of differing magic.