Many changes occurred when Kent invoked the True Names of his Legion.
First, he finally received the legendary name for the dungeon boss, which is "Eternal Wrath Legion." He had already suspected this because Vexthra had told him the story of the Night Riders, which ultimately led to the legend of the Chaos Dragon.
But it wasn't until then that he heard the name of his fourth legion.
In this instance, he could call them his third legion, considering he had yet to officially invoke the True Name of any of the Soul Sentinels, which excludes Elsa.
However, from what he knew, the Undead, the Lost Knights, the Soul Sentinels, and the Eternal Wrath were part of the legions that came from the future to defend the past.
And now that he had the official name for yet another legion, Kent became happy. However, there was something else that happened that made him happy to some extent.