All-in-all, four. Jason, Ruana, Dax and Riki are the ones that has control over the events.

[He took a breath before continuing for a bit more.]

There's a fifth one, Zo, but he's younger than all of them, and is the one in charge of whoever arrived here. He's not that good at it, though, so there's moments where he summoned someone who shouldn't be summoned, like Monobear.