Like Ragtime Mouse, True and its counterpart, False, are not regular enemies and are not designed to have their HP depleted. Attacking True indicates that the player answers True to that particular question, and the player can hit it even if the attack misses. If the player attacks all opponents with a group-cast ability then the battle will end as if the Ragtime Mouse is attacked and it will be as if the player has not answered the question.
Of the sixteen potential questions asked, half of the answers are True, including the final one.
While not summonable or fought, True appears alongside the Ragtime Mouse.