We're not quite sure what a Regnum is or why it is lost, but Lost Regnum from Ertain was a game that was worth finding on the TGS floor. An action-filled dungeon crawler, the game doesn't seem likely for release outside of Japan, but its frantic action did seem to make for a nice little import title.
Blazing fast, the gameplay in Lost Regnum is hack-and-slash, button-mashing goodness. The female character we played as (there are a variety of four character types to play as) had a large repertoire of ways to lay a beatdown, utilizing multiple buttons for attacks (the R trigger acted as a power modifier) that let you juggle enemies and toss them around the stage. Enemies could be drawn at each other, so those carrying a bow might hit their compatriots instead of you. The story mode can be played on your own, or you can bring a friend along for two-player dungeon hacking.