Chronologs were very ancient temporal devices used by the Praetorian Guard to cross portals through time. But most of these objects were destroyed before the crisis in Rome.
A very long time ago, the Wolves of the Praetorian Guard used to be the Keepers of the time passages and used chronologs to keep the timeline safe. But the chronologs were all destroyed when Lucifer rose as Caligula in Rome and posed too big of a threat to keep them on Earth - and they were proven right when the Wolves were betrayed by one of their own and were subdued to Lucifer's will.
However, one day, Romulus, the leader of the Hell Hounds, got his hands on the last chronolog, one that had been buried in the ground of Hell and dug up by one of the wolf dens, and told Lucifer about this. The Silver Blood saw his chance to eliminate of his potential enemies by using this device and asked Romulus to use it to re-write History.
Marrok, one of the rebel wolves in Hell, heard of this plan and managed to steal the artifact from Romulus, later giving the objects to Lawson and Bliss Llewellyn. As Romulus had found another way in the time passages however, Lawson and his friends were driven to use the last chronolog, and with Bliss's advice through the recollection of her mother's memories, were able to make it work and arrived in time to prevent the death of the Sabine women.
The chronolog activates with the pressure of a button on the side.
If the user commands orally, the chronolog will transport him in space to the destination required. However, to use it to travel in time, the user must pilot the three wands of the device to correctly choose the time and the coordinates of the destination.