As Cole was knocked out, the Librarian had chose to ignore one minisculr detail. Cole's Tome had been running since even before the interrogation in Angelo's possession. The sickeningly fresh vapor had not only seeped into Angelo's clothing and belongings, but into his skin itself. 

Thirty seconds at the construction site. 

A few minutes for the hotel and Capital roof.

Two seconds for Alex. 

And now a few dozen minutes of travel and almost ten minutes in Angelo's pocket. 

If he had not struck Cole so hard, perhaps the outcome would of changed. If Cole had not been on the verge of death already from the acts of the previous day, it wouldn't of mattered. But Cole's body was worn ragged, and already on it's last straws. It was a box of gunpowder that just needed one spark. Angelo unknowingly provided that spark. 

Cole's life ended with that blow to the temple and so did everyone else's life in the sewer. Perhaps Reddo and Eddie may escape with just severe burns and mutilated limbs which was certainly reparable by today's technology. But Angelo, the leader would have no such luck for he had held onto it for far too long. 

The tunnels suddenly roared into another onslaught of flames and a certain rebel leader was most certainly reduced to ashes. Thus ending the Legacy of Cole. 

A man, who in one day, both blew up part of the base of the Ultimatum and the seemingly untouchable Librarian himself. 

And was finally reunited with Silvia. So perhaps it was a happy ending for him, though we cannot say for sure the same thing about what's left of "The Librarian".