The Holy Light illuminates Truth. Truth is knowledge, and knowledge is power.
Sifo Grimaldi was one of the Lightist lieutenants in General Mordred Baldanes' army before the Azure Rebellion. When Mordred betrayed the kingdom, Grimaldi remained loyal to King Viktor Greymane. Thus, when Viktor Greymane was captured, Grimaldi went into hiding to escape the wrath of General Mordred.
When Tobijah Kruel discovered how to make Esarim of his own with the help of Esarim from Lordaeron, Sifo Grimaldi stepped forth from the shadows to pledge himself to the Church of Kruel. He was transformed into one of the Black Esarim.
Amarian Zeshuwal stumbled across him during the heretic host's march on Harrowdale, having accidentally triangulated him instead of her intended focal point, a treant named Talah.