From the Press Release
Today we're introducing the man, the myth, the legend -- the Highlander. The Highlander is a mercenary with a strong code of honor who uses his spear to dispense justice to all who stand in the way of the mission. He is the team leader who never holds back in battle and a invaluable damage dealer when traversing through Etria.
The Highlander
The uninformed might consider them mercenaries, since they are warriors available for hire, but a Highlander is more than that. Highlanders hew to a particular code, and won't blindly follow the orders of their paymasters if the situation calls for another approach. The particular Highlander in question was sent to Etria to look into a series of mysterious earthquakes, and it was in that investigation where he met Frederica.
The Highlander code emphasizes selflessness, and many of the Highlander's spear skills reflect that virtue. They generally sacrifice his own health to achieve their effects, though he can also recover some with every kill he scores in an efficient cycle of give-and-take.
To learn more, visit the official Atlus website.