Brief History

Shadrac is a mysterious entity, "an ancient evil", who empowers the ritual known as the Gathering of the Five. The ritual gathers five people who seek five magic gifts, randomly distributed among the participants. They are death,immortality, knowledge, madness and power. 
In the latest ritual a mercenary named Override ( Gregory Herd) received the 'gift' of death ... but not the way the participants figured. 
Shadrac took possession of Overide's body, gaining an avatar.

In this form, Shadrac resembled a skeleton consumed with mystical fire. The fire could not actually incinerate anything but caused intense pain to any who touched it. Shadrac could however melt through steel and concrete by slightly altering the spell. He also had superhuman strength and resistance to injury.

A conflict between the composite form of Shadrac and a man named Gray Dolman (whom had gained immortality in a 14th century Gathering) ended up turning Dolman to the third component of the form. Override returned to his normal self after that and no longer had any Shadrac's powers.
What happened to Dolman remains to be seen.
 
For more on Shadrac, see Gregory Herd (Override) and Gray Dolman.