Gaziel is an entity not actually encountered in the game, but mentioned two entries of Florentine's Journal.
Gaziel is a minor demon which, under the tutelage of Anarazel and with the help of his accomplice Fécor, is constantly moving treasures and riches from one place to another. His sole purpose is to hide and secure subterranean treasure and loot from the likes of men.
Entry, the afternoon of the 17th of January, 1330 ad.
The Temple of the Morning Star.
Following our initial experiment it is clear to me that magical means should be employed for safety. After many long hours of reading and speculating I have located the Seal and Sigil of the Minion Gaziel, one of the lesser powers. On the last crossing to the Tower, the Power Gaziel headed my call to guide Belial and I through the labyrinth void misleading the Ire as we travelled. Eventually we happened upon the Chamber of the Soulstone within the Realm of Sheol. Our Order now stand upon the threshold of the first of the great days. The first Shard of the Stone is now prepared. We are preparing for the next crossing. The stars are aligned and the portents are favourable. For the greater cause of the Power we walk to the Tower. For the first time we walk without fear of the Ire.
Entry, the evening of the 13th of January, 1420 ad.
Belial, again saving my life in the fire, has whispered to me of an otherworldly device that may aid the Order, but its location and power is shielded from him. We are therefore currently making the necessary plans to travel to Plymouth and there pay for passage on some merchant ship to Israel. The threat from our old Templar Order there does not bother me so much now that its existence is speculative. If we make Israel in good time I hope for us to meet there with the Minions Gaziel, Fécor and Anarazel and bargain with them for their aid in our search. They are adept in seeking out the impossible and locating what is hidden.
During my research on the triumvirate of Fécor, Gaziel and Anarazel, I couldn't really find many historical sources, such as grimoires or the likes, which would mention and elaborate on these creatures. As it is, my sole information so far has been mostly drawn from modern-day encyclopaedias on Demonology and Occultism.
According to the Dictionnaire Infernal, compiled by Jacques-Albin-Simon Collin de Plancy and published in 1825, Anarazel, aided by Fécor and Gaziel, shakes the foundations of houses ("ébranle les fondemens des maisons"), causes tempests ("excite les têmpetes"), rings the bells at midnight ("sonne les cloches à minuit"), makes ghosts appear (fait paraître les spectres") and inspires many other terrors ("inspire mille terreurs").