Culween

Culween is a character in the lore of Dota 2.

Biography
Culween must've invented or was involved in this creation of the spell, since Culween's possessive name is invoked when using it. Thus Culween must be a mage.

Seeing how the young Invoker (who existed during the earliest days when magic was once at its most potent form because 'twas still primarily a mnemonic art) learned the Forge Spirit spell alongside his nine other incantations, wielding them all with his rare and ancient sorcery of invoking, Culween must have existed during the golden age of Magic as well and thus this obscure magician must've been an ancient one too.

In Dota: Dragon's Blood
Culween may not be in Dota: Dragon's Blood, but their do make an appearance. Five of the Invoker's elemental minions were conjured to distract Filomena and the remaining Heroes from stopping his plan to see to the planet's facilitated cataclysm.

Save for Filomena who was busy using the Forge to repair the Mad Moon and Bram who was sent outside the Tower to watch for its destruction, the heroes managed to destroy them all. The last Forged Spirit was killed when Lina siphoned its flames from its body, suggesting that their fire is vital to them.

Not only is Culween absent, but the Invoker also doesn't appear to use the correct orbs (Two Exort, one Quas) to invoke them, instead having one of each of his three orbs out.

Inheritance
In his youth, the learned Culween's  alongside the nine other spells he currently has, using two Exort orbs and one Quas orb to invoke this spell for casting.

Immortality
Having existed during the old ages when magic was primarily mnemonic, Culween must've been quasi-immortal like the other ancient mages whom Invoker sourced his spells from.

That is, assuming that Culween is still alive today...

Magics
Much like the Invoker, Culween must have had his magic to up spells and wielded the energies of  and  to use invocations. Otherwise, Culween would not be able to conjure (also known as Culween's Most Cunning Fabrications  or Grief Elementals ) who are invoked using two Exort and one Quas. Embodying this strength of Exort's flame and the fortitude of Quas' ice, these elemental spirits are said to be created from naught. They also embody Exort's violence. They have the ability to spit out a that eats through enemy armor, as well as the implied ability to destroy the will, thus they are also known as "Ravagers of Armor and Will" when invoked. Perhaps their ability to ravage the will is the reason why they are called "Grief Elementals" as well. It seems that not all Forged Spirits look the same. This youthful Invoker's subservient elementals take the form of a young dragon hatchling.

Despite this Different appearance, this fiery Dragon whelp is still a Forged Spirit in nature, meaning that it's still an elemental spirit that is forged from naught. It's unknown why Forge Spirits can differ in appearance or what makes them take on different forms.

Regardless, this means that Forge Spirits do not have a constant form and may be shaped by unknown factors.