Casket of Fury

In this thread, I decided to discuss which of the Rage Spirits is most useful in battle. In my opinion, it's the Reaper, but in the early stages of the game, Zerok turns out to be more useful. I think Sleen is the least useful, as Zerok's initial ability is the most effective. Lina's ice ball is very helpful in battle, as it distracts enemies and deals decent damage. I'm interested in hearing your opinion.