From Lexicanum

Ghargatuloth is one of the most powerful Daemons of the Changer of Ways Tzeentch. He was present at the conclave on Thalassocres where Tzeentch spoke to his greatest daemons. Ghargatuloth is a daemon created from information. He is able to manifest himself through this media. His worshippers have been known to corrupt data machines for his cause. He has been banished twice by the Grey Knights, but continues to affect his plans from the warp. His true name is recorded in the Codicium Aeternum. Ghargatuloth is said to have created the Trail of Saint Evisser and use the body of Kelkannis Evisser‎ in order to bring about his re-manifestation.¹

Sources

• ¹:Grey Knights (Novel) by Ben Counter