The blood of Cronus, pure, raw, and unfiltered time. Normally, it’s inaccessible, but during the First War, members of the People of Darkness managed to gather a lot of it for the purpose of destroying the Saqalu.
It didn’t work – the Saqalu’s wings were able to hold it back – but it could not be dispersed or destroyed, and it does not degrade. In the end, the Saqalu used their own bodies and bones and blood to make the Wall of Time in Meginnah, behind which they hold that flood of chronos.
No one knows what to do with it. If it gets loose, there’s no knowing what it will do. The few loose drops of chronos anyone knows about destroyed what they touched, aging it to the point of complete and total death.