Ransom

Ransom is a unique "research", available at Age of Empires III, exclusively for European civilizations, at the Town Center.

Overview
The Explorer has a unique mechanic; in the event that he falls to 0 hitpoints, he will collapse in excruciating pain. Instead of recovering him via sending rescue units, the player has they choice to pay 100 coins as Ransom to whoever dealt the final blow (including Mother Nature).

Essentially, this technology is used to restore a fallen Hero or Explorer back to Town Center by paying 100.

It is not always a good idea to choose to Ransom the Explorer, as the 100 gold invested go to the player who dealt the fatal blow. This is especially the case at early-game, when resources are harder to collect, and a sudden boost of 100 gold can make the difference.