Nosgoth is a PC game, playable through Steam. It is a free-to-play, competitive online multiplayer title set in the Legacy of Kain universe. In a departure from the previous games, it features neither Kain or Raziel. Set in the time period after Raziel's execution in Soul Reaver, but before his return to the world as a Reaver of Souls, Nosgoth allows players to play co-operatively as vampires and humans in a war for supremacy and survival.
Partially devolved vampires of the clans battle against skilled human fighters who are starting to encroach on the fringes of the empire. The Emperor himself, Kain, is absent, having left his realm in the hands of his remaining lieutenants. The infighting of the clans which resulted from his departure, and the persecution of the leaderless Razielim, has been put aside temporarily to deal with the serious resurgent human threat to their dominance and their lives.
Details from Nosgoth are gradually being incorporated into this website. In the meantime, you can read how it fits into the Legacy of Kain storyline on the official website. Start with the Lore page, and then move on to the series of blog posts which explain the history of the factions in depth.