The Incarnate Titans were powerful Titans that could only be summoned with Power-bonded Amulets of intrepid design and power, when summoned the user would fuse with these Colossal Titans and therefore it was an extremely powerful version of power-bonding, while in human form the wielders of these Titans would be capable of learning physical skills enhanced by experiences of the Titan and its past wielders. There are Six of these Titans and they appear in the Defense Against The Nullifers series.
War with the Nullifers
The Incarnate Titans were the Six Knight guardians of Overlos and the Huntik (Spirit World) and their amulets were given to Lord Casterwill by Overlos, Casterwill gave the six Amulets to his loyal followers: the Champion of the Casterwill, the Elder Son of Casterwill, the Elder Daughter of Casterwill, the Younger Son of Casterwill, the Younger Daughter of Casterwill and The Betrayer.
Rise of the Betrayer
After the defeat of the Nullifers, The Betrayer turned his back on his Casterwill brothers and took off with his Knight which was one of the most powerful: Nelra the Celestial Knight, The Betrayer's Darkness and that of Void corrupted Nelra into a new form known only as the Demon Knight.